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Changes to Clojure in Version 1.10

1 Compatibility and Dependencies

1.1 Java

Clojure 1.10 now requires Java 8 or above. There were a number of updates related to this change and/or Java compatibility fixes for Java 8, 9, 10, and 11:

  • CLJ-2363 Bump to Java 8 as minimum requirement, update embedded ASM to 6.2, remove reliance on jsr166 jar, update javadoc links, and remove conditional logic.
  • CLJ-2367 ASM regression fix
  • CLJ-2284 Fix invalid bytecode generation for static interface method calls in Java 9+
  • CLJ-2066 Add reflection fallback for --illegal-access warnings in Java 9+
  • CLJ-2330 Fix brittle test that fails on Java 10 build due to serialization drift
  • CLJ-2374 Add type hint to address reflection ambiguity in JDK 11
  • CLJ-2375 Fix usage of deprecated JDK apis
  • CLJ-2414 Regression in reflectively finding default methods

1.2 Dependencies

Updated dependencies:

  • spec.alpha dependency to 0.2.176 - changes
  • core.specs.alpha dependency to 0.2.44 - changes

2 Features and major changes

2.1 Error messages

Clojure errors can occur in several distinct "phases" - reading source, macroexpansion, compilation, execution, and result printing. Clojure (and the REPL) now identify these phases in the exception and the message.

The read/macroexpand/compile phases produce a CompilerException and indicate the location in the caller source code where the problem occurred (previously macroexpansion reported the error in the macroexpansion stack). CompilerException now implements IExceptionInfo and ex-data will report exception data including the following (optional) keys:

  • :clojure.error/phase - phase (:read-source, :macro-syntax-check, :macroexpansion, :compile-syntax-check, :compilation, :execution, :read-eval-result, :print-eval-result)
  • :clojure.error/source - source file
  • :clojure.error/line - line in source file
  • :clojure.error/column - column of line in source file
  • :clojure.error/symbol - symbol being macroexpanded or compiled
  • :clojure.error/class - cause exception class symbol
  • :clojure.error/cause - cause exception message
  • :clojure.error/spec - explain-data for spec errors

clojure.main also contains two new functions: ex-triage and ex-str that can be used by external tools to mimic some or all of the Clojure repl reporting. ex-triage takes the output of Throwable->map and produces a concise analysis of the error phase, cause, etc (same keys as above). ex-str takes that analysis data and produces a message to print at the repl.

  • CLJ-2373 Detect phase and overhaul exception message and printing
  • CLJ-2415 Error cause should always be on 2nd line of error message
  • CLJ-2420 Refinement of error phases, ex-triage, execution error line reporting
  • CLJ-2427 CompilerException.toString() can throw if making message during initialization
  • CLJ-2430 Elevate phase in throwable data and conveyance for prepl
  • CLJ-2435 Include root cause class name in compilation and macroexpansion error phases
  • CLJ-2438 Demunge source symbol in execution error messages

2.2 Protocol extension by metadata

defprotocol has a new option :extend-via-metadata. When :extend-via-metadata is true, values can extend protocols by adding metadata where keys are fully-qualified protocol function symbols and values are function implementations. Protocol implementations are checked first for direct definitions (defrecord, deftype, reify), then metadata definitions, then external extensions (extend, extend-type, extend-protocol).

2.3 tap

tap is a shared, globally accessible system for distributing a series of informational or diagnostic values to a set of (presumably effectful) handler functions. It can be used as a better debug prn, or for facilities like logging etc.

tap> sends a value to the set of taps. Taps can be added with add-tap and will be called with any value sent to tap>. The tap function may (briefly) block (e.g. for streams) and will never impede calls to tap>, but blocking indefinitely may cause tap values to be dropped. If no taps are registered, tap> discards. Remove taps with remove-tap.

2.4 Read string capture mode

read+string is a new function that mimics read but also captures the string that is read and returns both the read value and the (whitespace-trimmed) read string. read+string requires a LineNumberingPushbackReader.

2.5 prepl (alpha)

prepl is a new stream-based REPL with structured output (suitable for programmatic use). Forms are read from the reader, evaluated, and return data maps for the return value (if successful), output to *out* (possibly many), output to *err* (possibly many), or tap> values (possibly many).

New functions in clojure.core.server:

  • prepl - the repl
  • io-prepl - a prepl bound to *in* and *out* suitable for use with the Clojure socket server
  • remote-prepl - a prepl that can be connected to a remote prepl over a socket

prepl is alpha and subject to change.

2.6 datafy and nav

clojure.datafy is a facility for object to data transformation. The datafy and nav functions can be used used to transform and (lazily) navigate through object graphs. The data transformation process can be influenced by consumers using protocols or metadata.

datafy is alpha and subject to change.

2.6 Other new functions in core

These functions have been added to match existing functions in ClojureScript to increase the portability of error-handling code:

  • ex-cause - extract the cause exception
  • ex-message - extract the cause message

This function has been added to construct a PrintWriter implementation whose behavior on flush and close is provided as functions:

  • PrintWriter-on - create a PrintWriter from flush-fn and close-fn

The following function has been added, extending resolve:

  • requiring-resolve - resolve or, if needed, require symbol's namespace, then resolve
  • serialized-require - like require but for use in asynchronous load uses

3 Enhancements

3.1 Error messages

  • CLJ-1279 Report correct arity count for function arity errors inside macros
  • CLJ-2386 Omit ex-info construction frames
  • CLJ-2394 Warn in pst that stack trace for syntax error failed before execution
  • CLJ-2396 Omit :in clauses when printing spec function errors if using default explain printer
  • CLJ-1797 Mention cljc in error when require fails
  • CLJ-1130 Improve error message when unable to match static method

3.2 Documentation

  • CLJ-2044 clojure.instant - add arglist meta for functions
  • CLJ-2257 proxy - fix typo
  • CLJ-2332 remove-tap - fix repetition
  • CLJ-2122 flatten - describe result as lazy

3.3 Performance

  • CLJ-1654 Reuse seq in some
  • CLJ-1366 The empty map literal is read as a different map each time
  • CLJ-2362 with-meta should return identity when new meta is identical to prior

3.4 Other enhancements

  • symbol can now take a var or a keyword argument
  • CLJ-1209 Print ex-data in clojure.test error reports
  • CLJ-2163 Add test for var serialization
  • CLJ-2417 sort and sort-by should retain meta

4 Fixes

4.1 Collections

  • CLJ-2297 PersistentHashMap leaks memory when keys are removed with without
  • CLJ-1587 PersistentArrayMap’s assoc doesn’t respect HASHTABLE_THRESHOLD
  • CLJ-2050 Remove redundant key comparisons in HashCollisionNode
  • CLJ-2089 Sorted colls with default comparator don’t check that first element is Comparable

4.2 API

  • CLJ-2031 clojure.walk/postwalk does not preserve MapEntry type objects
  • CLJ-2349 Report correct line number for uncaught ExceptionInfo in clojure.test
  • CLJ-1764 partition-by runs infinite loop when one element of infinite partition is accessed
  • CLJ-1832 unchecked-* functions have different behavior on primitive longs vs boxed Longs

4.3 Other

  • CLJ-1403 ns-resolve might throw ClassNotFoundException but should return nil
  • CLJ-2407 Fix bugs in Clojure unit tests
  • CLJ-1079 In reader, don't ignore explicit :line :col meta

Changes to Clojure in Version 1.9

1 New and Improved Features

1.1 spec

spec is a new core library for describing, validating, and testing the structure of data and functions.

For more information, see:

Note that spec is in alpha state and API compatibility is not guaranteed. Also, spec and the specs for the Clojure core API are distributed as external libraries that must be included to use Clojure.

1.2 Support for working with maps with qualified keys

Several enhancements have been made to add support for working with maps with qualified keys:

1.3 New predicates

Specs rely heavily on predicates and many new type and value oriented predicates have been added to clojure.core:

  • boolean?
  • int? pos-int? neg-int? nat-int?
  • double?
  • ident? simple-ident? qualified-ident?
  • simple-symbol? qualified-symbol?
  • simple-keyword? qualified-keyword?
  • bytes? (for byte[])
  • indexed?
  • uuid? uri?
  • seqable?
  • any?

1.4 More support for instants

More support has been added for the notion of instants in time:

  • Added a new protocol Inst for instant types
  • Inst is extended for java.util.Date
  • Inst is optionally extended for java.time.Instant in Java 1.8+
  • New functions that work for instants: inst?, inst-ms

1.5 Other new core functions

These are some other new functions in clojure.core:

  • bounded-count - a count that avoids realizing the entire collection beyond a bound
  • swap-vals! and reset-vals! - new atom functions that return both the old and new values (CLJ-1454)
  • halt-when - new transducer that ends transduction when pred is satisfied

1.6 Other reader enhancements

  • Can now bind *reader-resolver* to an impl of LispReader$Resolver to control the reader’s use of namespace interactions when resolving autoresolved keywords and maps.
  • Add new ## reader macro for symbolic values, and read/print support for double vals ##Inf, ##-Inf, ##NaN (CLJ-1074)

2 Enhancements

2.1 Spec syntax checking

If a macro has a spec defined via fdef, that spec will be checked at compile time. Specs have been defined for many clojure.core macros and errors will be reported for these based on the specs at compile time.

2.2 Documentation

  • doc will now report specs for functions with specs defined using fdef
  • doc can now be invoked with a fully-qualified keyword representing a spec name

2.3 Performance

  • Improved update-in performance
  • Optimized seq & destructuring
  • CLJ-2210 Cache class derivation in compiler to improve compiler performance
  • CLJ-2188 slurp - mark return type as String
  • CLJ-2070 clojure.core/delay - improve performance
  • CLJ-1917 Reducing seq over string should call String/length outside of loop
  • CLJ-1901 amap - should call alength only once
  • CLJ-1224 Record instances now cache hasheq and hashCode like maps
  • CLJ-99 min-key and max-key - evaluate k on each arg at most once

2.4 Other enhancements

  • Added Var serialization for identity, not value
  • into now has a 0-arity (returns []) and 1-arity (returns the coll that's passed)
  • CLJ-2184 Propagate meta in doto forms to improve error reporting
  • CLJ-1744 Clear unused locals, which can prevent memory leaks in some cases
  • CLJ-1673 clojure.repl/dir-fn now works on namespace aliases
  • CLJ-1423 Allow vars to be invoked with infinite arglists (also, faster)

3 Fixes

3.1 Security

  • CLJ-2204 Disable serialization of proxy classes to avoid potential issue when deserializing

3.2 Docs

  • CLJ-2170 fix improperly located docstrings
  • CLJ-2156 clojure.java.io/copy - doc char[] support
  • CLJ-2104 clojure.pprint docstring - fix typo
  • CLJ-2051 clojure.instant/validated docstring - fix typo
  • CLJ-2039 deftype - fix typo in docstring
  • CLJ-2028 filter, filterv, remove, take-while - fix docstrings
  • CLJ-1918 await - improve docstring re shutdown-agents
  • CLJ-1873 require, *data-readers* - add .cljc files to docstrings
  • CLJ-1859 zero?, pos?, neg? - fix docstrings
  • CLJ-1837 index-of, last-index-of - clarify docstrings
  • CLJ-1826 drop-last - fix docstring
  • CLJ-1159 clojure.java.io/delete-file - improve docstring

3.3 Other fixes

  • clojure.core/Throwable->map formerly returned StackTraceElements which were later handled by the printer. Now the StackTraceElements are converted to data such that the return value is pure Clojure data, as intended.
  • CLJ-2091 clojure.lang.APersistentVector#hashCode is not thread-safe
  • CLJ-2077 Clojure can't be loaded from the boot classpath under java 9
  • CLJ-2048 Specify type to avoid ClassCastException when stack trace is elided by JVM
  • CLJ-1914 Fixed race condition in concurrent range realization
  • CLJ-1887 IPersistentVector.length() - implement missing method
  • CLJ-1870 Fixed reloading a defmulti removes metadata on the var
  • CLJ-1860 Make -0.0 hash consistent with 0.0
  • CLJ-1841 bean - iterator was broken
  • CLJ-1793 Clear 'this' before calls in tail position
  • CLJ-1790 Fixed error extending protocols to Java arrays
  • CLJ-1714 using a class in a type hint shouldn’t load the class
  • CLJ-1705 vector-of - fix NullPointerException if given unrecognized type
  • CLJ-1398 clojure.java.javadoc/javadoc - update doc urls
  • CLJ-1371 Numbers.divide(Object, Object) - add checks for NaN
  • CLJ-1358 doc - does not expand special cases properly (try, catch)
  • CLJ-1242 equals doesn't throw on sorted collections
  • CLJ-700 contains?, get, and find broken for transient collections

Changes to Clojure in Version 1.8

1 New and Improved Features

1.1 Direct Linking

Direct linking can be enabled with -Dclojure.compiler.direct-linking=true

Direct linking allows functions compiled with direct linking on to make direct static method calls to most other functions, instead of going through the var and the Fn object. This can enable further optimization by the jit, at a cost in dynamism. In particular, directly-linked calls will not see redefinitions.

With this change, clojure.core itself is compiled with direct linking and therefore other namespaces cannot redefine core fns and have those redefinitions seen by core code.

A new metadata key ^:redef is provided. A function declared with this key can be redefined and will never be direct linked. Also, functions declared as ^:dynamic will never be direct linked.

1.2 String Functions

Several new string functions were added to clojure.string to increase portability and reduce the need for Java interop calls:

  • index-of - search for the index of a char or string in a string

  • last-index-of - search for the index of a char or string backwards in a string

  • starts-with? - true if string starts with a substring

  • ends-with? - true if string ends with a substring

  • includes? - true if string includes a substring

  • CLJ-1449

1.3 Socket Server and REPL

The Clojure runtime now has the ability to start a socket server at initialization based on system properties. One expected use for this is serving a socket-based REPL, but it also has many other potential uses for dynamically adding server capability to existing programs without code changes.

A socket server will be started for each JVM system property like clojure.server.<server-name>. The value for this property is an edn map representing the configuration of the socket server with the following properties:

  • address - host or address, defaults to loopback
  • port - positive integer, required
  • accept - namespaced symbol of function to invoke on socket accept, required
  • args - sequential collection of args to pass to accept
  • bind-err - defaults to true, binds *err* to socket out stream
  • server-daemon - defaults to true, socket server thread doesn't block exit
  • client-daemon - defaults to true, socket client thread doesn't block exit

Additionally, there is a repl function provided that is slightly customized for use with the socket server in clojure.core.server/repl.

Following is an example of starting a socket server with a repl listener. This can be added to any existing Clojure program to allow it to accept external REPL clients.

-Dclojure.server.repl="{:port 5555 :accept clojure.core.server/repl}"

An example client you can use to connect to this socket repl is telnet:

$ telnet 127.0.0.1 5555
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
user=> (println "hello")
hello

See:

2 Enhancements

2.1 Error handling

  • CLJ-1778 let-bound namespace-qualified bindings should throw (if not map destructuring)
  • CLJ-1456 Compiler now errors if too few or too many arguments to throw
  • CLJ-1282 quote now throws if passed more or less than one arg
  • CLJ-1210 Improved error message for (clojure.java.io/reader nil)

2.2 Documentation strings

  • CLJ-1060 'list*' returns not a list
  • CLJ-1722 Typo in the docstring of 'with-bindings'
  • CLJ-1769 Docstrings for *' and +' refer to * and +
  • CLJ-1414 sort and sort-by now indicate sort is stable in docstring

2.3 Performance

  • CLJ-703 Improve writeClassFile performance
  • CLJ-1765 areduce performance improvements
  • CLJ-1724 Remove unnecessary call to seq() in LazySeq.hashCode()
  • CLJ-1295 Improved array-map dissoc performance
  • CLJ-1277 Speed up printing of time instants with type hints
  • CLJ-1259 Speed up pprint and cl-format with type hints
  • CLJ-668 Improve slurp performance by using StringWriter and jio/copy

2.4 Other enhancements

  • CLJ-1208 Optionally require namespace on defrecord class init
  • CLJ-1823 Document new :load-ns option to defrecord/deftype
  • CLJ-1810 ATransientMap now marked public
  • CLJ-1653 str of an empty list should be "()"
  • CLJ-1567 Removed unused local in condp implementation
  • CLJ-1351 Unused swapThunk method was being emitted for fns with keyword callsites
  • CLJ-1329 Removed unused local in PersistentVector.cons()
  • CLJ-1831 Add clojure.core/map-entry? predicate
  • CLJ-1845 Make clojure.core/load dynamic so it can be redef'ed even with direct linking

3 Bug Fixes

  • CLJ-130 Namespace metadata lost in AOT compile
  • CLJ-1134 star-directive in clojure.pprint/cl-format with at-prefix ("~n@*") does not obey its specification
  • CLJ-1137 Metadata on a def gets evaluated twice
  • CLJ-1157 Classes generated by gen-class aren't loadable from remote codebase
  • CLJ-1225 quot overflow issues around Long/MIN_VALUE for BigInt
  • CLJ-1313 Correct a few unit tests
  • CLJ-1319 array-map fails lazily if passed an odd number of arguments
  • CLJ-1361 pprint with code-dispatch incorrectly prints a simple ns macro call
  • CLJ-1390 pprint a GregorianCalendar results in Arity exception
  • CLJ-1399 field name unmunged when recreating deftypes serialized into bytecode
  • CLJ-1485 clojure.test.junit/with-junit-output doesn't handle multiple expressions
  • CLJ-1528 clojure.test/inc-report-counter is not thread-safe
  • CLJ-1533 invokePrim path does not take into account var or form meta
  • CLJ-1562 some->,some->>,cond->,cond->> and as-> doesn't work with (recur)
  • CLJ-1565 pprint produces infinite output for a protocol
  • CLJ-1588 StackOverflow in clojure.test macroexpand with are and anon fn
  • CLJ-1644 into-array fails for sequences starting with nil
  • CLJ-1645 protocol class does not set the source file
  • CLJ-1657 proxy bytecode calls super methods of abstract classes
  • CLJ-1659 compile leaks files
  • CLJ-1761 clojure.core/run! does not always return nil per docstring
  • CLJ-1782 Spelling mistake in clojure.test/use-fixtures
  • CLJ-1785 Reader conditionals throw when returning nil
  • CLJ-1766 Serializing+deserializing lists breaks their hash
  • CLJ-1609 Edge case in Reflector's search for a public method declaration
  • CLJ-1586 Compiler doesn't preserve metadata for LazySeq literals
  • CLJ-1232 Functions with non-qualified return type hints will now work without import from other namespace
  • CLJ-1812 Fix test failure on windows due to line endings
  • CLJ-1380 3-arg ExceptionInfo constructor permitted nil data
  • CLJ-1226 set! of a deftype field using field-access syntax caused ClassCastException
  • Records and types without fields eval to empty map
  • CLJ-1827 Fix reflection warning introduced in CLJ-1259
  • CLJ-1453 Ensure that all Iterator implementations throw NoSuchElementException on next() when exhausted
  • CLJ-1868 Avoid compiler NPE when checking class return type

Changes to Clojure in Version 1.7

1 Compatibility Notes

Please be aware of the following issues when upgrading to Clojure 1.7.

Seqs on Java iterators that return the same mutating object

Seqs are fundamentally incompatible with Java iterators that return the same mutating object on every call to next(). Some Clojure libraries incorrectly rely on calling seq on such iterators.

In 1.7, iterator-seqs are chunked, which will cause many of these incorrect usages to return incorrect results immediately.

The seq and iterator-seq docstrings have been updated to include an explicit warning. Libraries that incorrectly use seq and iterator-seq will need to be fixed before running against 1.7.

Thread owner check removed on transients

Prior to Clojure 1.7, transients would allow modification only from the thread that created the transient. This check has been removed. It is still a requirement that transients should be updated by only a single thread at a time.

This constraint was relaxed to allow transients to be used in cases where code is multiplexed across multiple threads in a pool (such as go blocks in core.async).

keys/vals require custom map type to implement Iterable

Invoking keys or vals on a custom map type that implements IPersistentMap will now use the Iterable iterator() method instead of accessing entries via the seq of the map. There have been no changes in the type hierarchy (IPersistentMap has always extended Iterable) but former map-like instances may have skipped implementing this method in the past.

2 New and Improved Features

2.1 Transducers

Transducers is a new way to decouple algorithmic transformations from their application in different contexts. Transducers are functions that transform reducing functions to build up a "recipe" for transformation.

Also see: http://clojure.org/transducers

Many existing sequence functions now have a new arity (one fewer argument than before). This arity will return a transducer that represents the same logic but is independent of lazy sequence processing. Functions included are:

  • map
  • mapcat
  • filter
  • remove
  • take
  • take-while
  • drop
  • drop-while
  • take-nth
  • replace
  • partition-by
  • partition-all
  • keep
  • keep-indexed
  • map-indexed
  • distinct
  • interpose

Additionally some new transducer functions have been added:

  • cat - concatenates the contents of each input
  • dedupe - removes consecutive duplicated values
  • random-sample - returns items from coll with random probability

And this function can be used to make completing transforms:

  • completing

There are also several new or modified functions that can be used to apply transducers in different ways:

  • sequence - takes a transformation and a coll and produces a lazy seq
  • transduce - reduce with a transformation (eager)
  • eduction - returns a reducible/iterable of applications of the transducer to items in coll. Applications are re-performed with every reduce/iterator.

There have been a number of internal changes to support transducers:

  • volatiles - there are a new set of functions (volatile!, vswap!, vreset!, volatile?) to create and use volatile "boxes" to hold state in stateful transducers. Volatiles are faster than atoms but give up atomicity guarantees so should only be used with thread isolation.
  • array iterators - added support for iterators over arrays
  • conj can be used as a reducing function and will conj to []

Some related issues addressed during development:

2.2 Reader Conditionals

Reader Conditionals are a new capability to support portable code that can run on multiple Clojure platforms with only small changes. In particular, this feature aims to support the increasingly common case of libraries targeting both Clojure and ClojureScript.

Code intended to be common across multiple platforms should use a new supported file extension: ".cljc". When requested to load a namespace, the platform-specific file extension (.clj, .cljs) will be checked prior to .cljc.

A new reader form can be used to specify "reader conditional" code in cljc files (and only cljc files). Each platform defines a feature identifying the platform (:clj, :cljs, :cljr). The reader conditional specifies code that is read conditionally based on the feature. The REPL also allows reader conditionals.

Form #? takes a list of alternating feature and expression. These are checked like cond and the selected expression is read and returned. Other branches are read but skipped. If no branch is selected, the reader reads nothing (not nil, but literally as if reading no form). An optional :default branch can be used as a fallthrough.

Reader conditional with 2 features and a default:

#?(:clj     Double/NaN
   :cljs    js/NaN
   :default nil)

There is also a reader conditional splicing form. The evaluated expression should be sequential and will be spliced into the surrounded code, similar to unquote-splicing.

For example:

[1 2 #?@(:clj [3 4] :cljs [5 6])]

This form would read as [1 2 3 4] on Clojure, [1 2 5 6] on ClojureScript, and [1 2] on any other platform. Splicing is not allowed at the top level.

Additionally, the reader can now be invoked with options for the features to use and how to interpret reader conditionals. By default, reader conditionals are not allowed, but that can be turned on, or a "preserve" mode can be used to preserve all branches (most likely useful for tooling or source transforms).

In the preserve mode, the reader conditional itself and any tagged literals within the unselected branches are returned as tagged literal data.

For more information, see: http://dev.clojure.org/display/design/Reader+Conditionals

2.3 Keyword and Symbol Construction

In response to issues raised in CLJ-1439, several changes have been made in symbol and keyword construction:

  1. The main bottleneck in construction of symbols (which also occurs inside keywords) was interning of the name and namespace strings. This interning has been removed, resulting in a performance increase.

  2. Keywords are cached and keyword construction includes a cache check. A change was made to only clear the cache reference queue when there is a cache miss.

2.4 Warn on Boxed Math

One source of performance issues is the (unintended) use of arithmetic operations on boxed numbers. To make detecting the presence of boxed math easier, a warning will now be emitted about boxed math if *unchecked-math* is set to :warn-on-boxed (any truthy value will enable unchecked-math, only this specific value enables the warning).

Example use:

user> (defn plus-2 [x] (+ x 2))  ;; no warning, but boxed
#'user/plus-2
user> (set! *unchecked-math* :warn-on-boxed)
true
user> (defn plus-2 [x] (+ x 2)) ;; now we see a warning
Boxed math warning, NO_SOURCE_PATH:10:18 - call: public static java.lang.Number
clojure.lang.Numbers.unchecked_add(java.lang.Object,long).
#'user/plus-2
user> (defn plus-2 [^long x] (+ x 2)) ;; use a hint to avoid boxing
#'user/plus-2

2.5 update - like update-in for first level

update is a new function that is like update-in specifically for first-level keys:

(update m k f args...)

Example use:

user> (update {:a 1} :a inc)
{:a 2}
user> (update {:a 1} :a + 2)
{:a 3}
user> (update {} :a identity)  ;; missing returns nil
{:a nil}

2.6 Faster reduce and iterator paths

Several important Clojure functions now return sequences that also contain fast reduce() (or in some cases iterator()) paths. In many cases, the new implementations are also faster for lazy sequences

  • repeat - now implements IReduce
  • cycle - implements IReduceInit
  • iterate - implements IReduceInit
  • range - implements IReduce, specialized case handles common case of all longs
  • keys - iterates directly over the keys of a map, without seq or MapEntry allocation
  • vals - iterates directly over the vals of a map, without seq or MapEntry allocation
  • iterator-seq - creates a chunked sequence when previously it was unchunked

Additionally, hash-maps and hash-sets now provide iterators that walk the data structure directly rather than via a sequence.

A new interface (IMapIterable) for direct key and val iterators on maps was added. External data structures can use this interface to provide direct key and val iterators via keys and vals.

These enhancements are particularly effective when used in tandem with transducers via transduce, sequence, into, and eduction.

2.7 Printing as data

There have been enhancements in how the REPL prints values without a print-method, specifically Throwable and the fallthrough Object case. Both cases now print in a tagged literal data form that can be read by the reader.

Unhandled objects print with the class, hash code, and toString:

user=> *ns*
#object[clojure.lang.Namespace 0x55aa628 "user"]

Thrown exceptions will still be printed in the normal way by the default REPL but printing them to a stream will show a different form:

user=> (/ 1 0)
ArithmeticException Divide by zero  clojure.lang.Numbers.divide (Numbers.java:158)
user=> (println *e)
#error {
 :cause Divide by zero
 :via
 [{:type java.lang.ArithmeticException
   :message Divide by zero
   :at [clojure.lang.Numbers divide Numbers.java 158]}]
 :trace
 [[clojure.lang.Numbers divide Numbers.java 158]
  [clojure.lang.Numbers divide Numbers.java 3808]
  ;; ... elided frames
  ]}

Additionally, there is a new function available to obtain a Throwable as map data: Throwable->map.

2.8 run!

run! is a new function that takes a side effect reducing function and runs it for all items in a collection via reduce. The accumulator is ignored and nil is returned.

(run! println (range 10))

3 Enhancements

3.1 Error messages

  • CLJ-1261 Invalid defrecord results in exception attributed to consuming ns instead of defrecord ns
  • CLJ-1297 Give more specific hint if namespace with "-" not found to check file uses "_"

3.2 Documentation strings

  • CLJ-1417 clojure.java.io/input-stream has incorrect docstring
  • CLJ-1357 Fix typo in gen-class doc-string
  • CLJ-1479 Fix typo in filterv example
  • CLJ-1480 Fix typo in defmulti docstring
  • CLJ-1477 Fix typo in deftype docstring
  • CLJ-1478 Fix typo in clojure.main usage
  • CLJ-1738 Clarify usage on Java iterators in seq and iterator-seq

3.3 Performance

  • CLJ-1430 Improve performance of partial with more unrolling
  • CLJ-1384 clojure.core/set should use transients for better performance
  • CLJ-1429 Cache unknown multimethod value default dispatch
  • CLJ-1529 Reduce compile times by avoiding unnecessary calls to Class.forName()
  • CLJ-1546 vec is now faster on almost all inputs
  • CLJ-1618 set is now faster on almost all inputs
  • CLJ-1695 Fixed reflection call in variadic vector-of constructor

3.4 Other enhancements

  • CLJ-1191 Improve apropos to show some indication of namespace of symbols found
  • CLJ-1378 Hints don't work with #() form of function
  • CLJ-1498 Removes owner-thread check from transients - this check was preventing some valid usage of transients in core.async where a transient is created on one thread and then used again in another pooled thread (while still maintaining thread isolation).
  • CLJ-803 Extracted IAtom interface implemented by Atom.
  • CLJ-1315 Don't initialize classes when importing them
  • CLJ-1330 Class name clash between top-level functions and defn'ed ones
  • CLJ-1349 Update to latest test.generative and add dependency on test.check
  • CLJ-1546 vec now works with things that only implement Iterable or IReduceInit
  • CLJ-1618 set now works with things that only implement Iterable or IReduceInit
  • CLJ-1633 PersistentList/creator doesn't handle ArraySeqs correctly
  • CLJ-1589 Clean up unused paths in InternalReduce
  • CLJ-1677 Add setLineNumber() to LineNumberingPushbackReader
  • CLJ-1667 Change test to avoid using hard-coded socket port
  • CLJ-1683 Change reduce tests to better catch reduce without init bugs

4 Bug Fixes

  • CLJ-1362 Reduce broken on some primitive vectors
  • CLJ-1388 Equality bug on records created with nested calls to map->record
  • CLJ-1274 Unable to set compiler options via system properties except for AOT compilation
  • CLJ-1241 NPE when AOTing overrided clojure.core functions
  • CLJ-1185 reductions does not check for reduced value
  • CLJ-1039 Using def with metadata {:type :anything} throws ClassCastException during printing
  • CLJ-887 Error when calling primitive functions with destructuring in the arg vector
  • CLJ-823 Piping seque into seque can deadlock
  • CLJ-738 <= is incorrect when args include Double/NaN
  • CLJ-1408 Make cached string value of Keyword and Symbol transient
  • CLJ-1466 clojure.core/bean should implement Iterable
  • CLJ-1578 Make refer of Clojure core function not throw exception on reload
  • CLJ-1501 LazySeq equals() should not use equiv() logic
  • CLJ-1572 into (and other fns that rely on reduce) require only IReduceInit
  • CLJ-1619 PersistentVector now directly implements reduce without init
  • CLJ-1580 Transient collections should guarantee thread visibility
  • CLJ-1590 Some IReduce/IReduceInit implementors don't respect reduced
  • CLJ-979 Clojure resolves to wrong deftype classes when AOT compiling or reloading
  • CLJ-1636 Fix intermittent SeqIterator problem by removing use of this as a sentinel
  • CLJ-1637 Fix regression from CLJ-1546 that broke vec on MapEntry
  • CLJ-1663 Fix regression from CLJ-979 for DynamicClassLoader classloader delegation
  • CLJ-1604 Fix error from AOT'ed code defining a var with a clojure.core symbol name
  • CLJ-1561 Fix incorrect line number reporting for error locations
  • CLJ-1568 Fix incorrect line number reporting for error locations
  • CLJ-1638 Fix regression from CLJ-1546 removed PersistentVector.create(List) method
  • CLJ-1681 Fix regression from CLJ-1248 (1.6) in reflection warning with literal nil argument
  • CLJ-1648 Use equals() instead of == when resolving Symbol
  • CLJ-1195 emit-hinted-impl expands to ns-qualified invocation of fn
  • CLJ-1237 reduce of sequence that switches between chunked and unchunked many times throws StackOverflow

Changes to Clojure in Version 1.6

CONTENTS

1 Compatibility and Dependencies

1.1 JDK Version Update

Clojure now builds with Java SE 1.6 and emits bytecode requiring Java SE 1.6 instead of Java SE 1.5. [CLJ-1268]

1.2 ASM Library Update

The embedded version of the ASM bytecode library has been upgraded to ASM 4.1. [CLJ-713]

1.3 Promoted "Alpha" Features

The following features are no longer marked Alpha in Clojure:

  • Watches - add-watch, remove-watch
  • Transients - transient, persistent!, conj!, assoc!, dissoc!, pop!, disj!
  • Exception data - ex-info, ex-data
  • Promises - promise, deliver
  • Records - defrecord
  • Types - deftype
  • Pretty-print tables - print-table

2 New and Improved Features

2.1 Java API

The clojure.java.api package provides a minimal interface to bootstrap Clojure access from other JVM languages. It does this by providing:

  1. The ability to use Clojure's namespaces to locate an arbitrary var, returning the var's clojure.lang.IFn interface.
  2. A convenience method read for reading data using Clojure's edn reader.

IFns provide complete access to Clojure's APIs. You can also access any other library written in Clojure, after adding either its source or compiled form to the classpath.

The public Java API for Clojure consists of the following classes and interfaces:

  • clojure.java.api.Clojure
  • clojure.lang.IFn

All other Java classes should be treated as implementation details, and applications should avoid relying on them.

To look up and call a Clojure function:

IFn plus = Clojure.var("clojure.core", "+");
plus.invoke(1, 2);

Functions in clojure.core are automatically loaded. Other namespaces can be loaded via require:

IFn require = Clojure.var("clojure.core", "require");
require.invoke(Clojure.read("clojure.set"));

IFns can be passed to higher order functions, e.g. the example below passes plus to read:

IFn map = Clojure.var("clojure.core", "map");
IFn inc = Clojure.var("clojure.core", "inc");
map.invoke(inc, Clojure.read("[1 2 3]"));

Most IFns in Clojure refer to functions. A few, however, refer to non-function data values. To access these, use deref instead of fn:

IFn printLength = Clojure.var("clojure.core", "*print-length*");
Clojure.var("clojure.core", "deref").invoke(printLength);

2.2 Map destructuring extended to support namespaced keys

In the past, map destructuring with :keys and :syms would not work with maps containing namespaced keys or symbols. The :keys and :syms forms have been updated to allow them to match namespaced keys and bind to a local variable based on the name.

Examples:

(let [m {:x/a 1, :y/b 2}
      {:keys [x/a y/b]} m]
  (+ a b))

(let [m {'x/a 1, 'y/b 2}
      {:syms [x/a y/b]} m]
  (+ a b))

Additionally, the :keys form can now take keywords instead of symbols. This provides support specifically for auto-resolved keywords:

(let [m {:x/a 1, :y/b 2}
      {:keys [:x/a :y/b]} m]
  (+ a b))

(let [m {::x 1}
      {:keys [::x]} m]
  x)

2.3 New "some" operations

Many conditional functions rely on logical truth (where "falsey" values are nil or false). Sometimes it is useful to have functions that rely on "not nilness" instead. These functions have been added to support these cases [CLJ-1343]:

  • some? - same as (not (nil? x))
  • if-some - like if-let, but checks (some? test) instead of test
  • when-some - like when-let, but checks (some? test) instead of test

2.4 Hashing

Clojure 1.6 provides new hashing algorithms for primitives and collections, accessible via IHashEq/hasheq (in Java) or the clojure.core/hash function (in Clojure). In general, these changes should be transparent to users, except hash codes used inside hashed collections like maps and sets will have better properties.

Hash codes returned by the Java .hashCode() method are unchanged and continue to match Java behavior or conform to the Java specification as appropriate.

Any collections implementing IHashEq or wishing to interoperate with Clojure collections should conform to the hashing algorithms specified in http://clojure.org/data_structures#hash and use the new function mix-collection-hash for the final mixing operation. Alternatively, you may call the helper functions hash-ordered-coll and hash-unordered-coll.

Any details of the current hashing algorithm not specified on that page should be considered subject to future change.

Related tickets for dev and regressions:

  • CLJ-1328 Make several Clojure tests independent of ordering
  • CLJ-1331 Update primitive vectors to use Murmur3 hash
  • CLJ-1335 Update hash for empty PersistentList and LazySeq
  • CLJ-1336 Make hashing mixing functions available in Clojure
  • CLJ-1338 Make Murmur3 class public
  • CLJ-1344 Update mapHasheq to call Murmur3 algorithm
  • CLJ-1348 Add hash-ordered-coll and hash-unordered-coll
  • CLJ-1355 Restore cached hashCode for Symbol and (uncached) hashCode for Keyword
  • CLJ-1365 Add type hints for new collection hash functions

2.5 bitops

A new unsigned-bit-shift-right (Java's >>>) has been added to the core library. The shift distance is truncated to the least 6 bits (per the Java specification for long >>>).

Examples: (unsigned-bit-shift-right 2r100 1) ;; 2r010 (unsigned-bit-shift-right 2r100 2) ;; 2r001 (unsigned-bit-shift-right 2r100 3) ;; 2r000

2.6 clojure.test

Added a new clojure.test/test-vars function that takes a list of vars, groups them by namespace, and runs them with their fixtures.

3 Enhancements

3.1 Printing

  • CLJ-908 Print metadata for functions when print-meta is true and remove errant space at beginning.
  • CLJ-937 pprint cl-format now supports E, F, and G formats for ratios.

3.2 Error messages

  • CLJ-1248 Include type information in reflection warning messages
  • CLJ-1099 If non-seq passed where seq is needed, error message now is an ExceptionInfo with the instance value, retrievable via ex-data.
  • CLJ-1083 Fix error message reporting for "munged" function names (like a->b).
  • CLJ-1056 Handle more cases and improve error message for errors in defprotocol definitions.
  • CLJ-1102 Better handling of exceptions with empty stack traces.
  • CLJ-939 Exceptions thrown in the top level ns form are reported without file or line number.

3.3 Documentation strings

  • CLJ-1164 Fix typos in clojure.instant/validated and other internal instant functions.
  • CLJ-1143 Correct doc string for ns macro.
  • CLJ-196 Clarify value of file is undefined in the REPL.
  • CLJ-1228 Fix a number of spelling errors in namespace and doc strings.
  • CLJ-835 Update defmulti doc to clarify expectations for hierarchy argument.
  • CLJ-1304 Fix minor typos in documentation and comments
  • CLJ-1302 Mention that keys and vals order are consistent with seq order

3.4 Performance

  • CLJ-858 Improve speed of STM by removing System.currentTimeMillis.
  • CLJ-669 clojure.java.io/do-copy: use java.nio for Files
  • commit Reduce overhead of protocol callsites by removing unneeded generated cache fields.

3.5 Other enhancements

  • CLJ-908 Make default-data-reader-fn set!-able in REPL, similar to data-readers.
  • CLJ-783 Make clojure.inspector/inspect-tree work on sets.
  • CLJ-896 Make browse-url aware of xdg-open.
  • CLJ-1160 Fix clojure.core.reducers/mapcat does not stop on reduced? values.
  • CLJ-1121 -> and ->> have been rewritten to work with a broader set of macros.
  • CLJ-1105 clojure.walk now supports records.
  • CLJ-949 Removed all unnecessary cases of sneakyThrow.
  • CLJ-1238 Allow EdnReader to read foo// (matches LispReader behavior).
  • CLJ-1264 Remove uses of _ as a var in the Java code (causes warning in Java 8).
  • CLJ-394 Add record? predicate.
  • CLJ-1200 ArraySeq dead code cleanup, ArraySeq_short support added.
  • CLJ-1331 Primitive vectors should implement hasheq and use new hash algorithm
  • CLJ-1354 Make APersistentVector.SubVector public so other collections can access
  • CLJ-1353 Make awt run headless during the build process

4 Bug Fixes

  • CLJ-1018 Make range consistently return infinite sequence of start with a step of 0.
  • CLJ-863 Make interleave return () on 0 args and identity on 1 args.
  • CLJ-1072 Update internal usages of the old metadata reader syntax to new syntax.
  • CLJ-1193 Make bigint and biginteger functions work on double values outside long range.
  • CLJ-1154 Make Compile.java flush but not close stdout so errors can be reported.
  • CLJ-1161 Remove bad version.properties from sources jar.
  • CLJ-1175 Fix invalid behavior of Delay/deref if an exception is thrown - exception will now be rethrown on subsequent calls and not enter a corrupted state.
  • CLJ-1171 Fix several issues with instance? to make it consistent when used with apply.
  • CLJ-1202 Protocol fns with dashes may get incorrectly compiled into field accesses.
  • CLJ-850 Add check to emit invokePrim with return type of double or long if type-hinted.
  • CLJ-1177 clojure.java.io URL to File coercion corrupts path containing UTF-8 characters.
  • CLJ-1234 Accept whitespace in Record and Type reader forms (similar to data literals).
  • CLJ-1233 Allow ** as a valid symbol name without triggering dynamic warnings.
  • CLJ-1246 Add support to clojure.reflect for classes with annotations.
    • CLJ-1184 Evaling #{do ...} or [do ...] is treated as do special form.
  • CLJ-1090 Indirect function calls through Var instances fail to clear locals.
  • CLJ-1076 pprint tests fail on Windows, expecting \n.
  • CLJ-766 Make into-array work consistently with short-array and byte-array on bigger types.
  • CLJ-1285 Data structure invariants are violated after persistent operations when collision node created by transients.
  • CLJ-1222 Multiplication overflow issues around Long/MIN_VALUE
  • CLJ-1118 Inconsistent numeric comparison semantics between BigDecimals and other numerics
  • CLJ-1125 Clojure can leak memory in a servlet container when using dynamic bindings or STM transactions.
  • CLJ-1082 Subvecs of primitve vectors cannot be reduced
  • CLJ-1301 Case expressions use a mixture of hashCode and hasheq, potentially leading to missed case matches when these differ.
  • CLJ-983 proxy-super does not restore original binding if call throws exception
  • CLJ-1176 clojure.repl/source errors when read-eval bound to :unknown
  • CLJ-935 clojure.string/trim uses different definition of whitespace than triml and trimr
  • CLJ-1058 StackOverflowError on exception in reducef for PersistentHashMap fold
  • CLJ-1328 Fix some tests in the Clojure test suite to make their names unique and independent of hashing order
  • CLJ-1339 Empty primitive vectors throw NPE on .equals with non-vector sequential types
  • CLJ-1363 Field access via .- in reflective case does not work
  • CLJ-944 Compiler gives constant collections types which mismatch their runtime values
  • CLJ-1387 reduce-kv on large hash maps ignores reduced result

Changes to Clojure in Version 1.5.1

  • fix for leak caused by ddc65a96fdb1163b

Changes to Clojure in Version 1.5

CONTENTS

 1 Deprecated and Removed Features
    1.1 Clojure 1.5 reducers library requires Java 6 or later
 2 New and Improved Features
    2.1 Reducers
    2.2 Reader Literals improved
    2.3 clojure.core/set-agent-send-executor!, set-agent-send-off-executor!, and send-via
    2.4 New threading macros
    2.5 Column metadata captured by reader
    2.6 gen-class improvements
    2.7 Support added for marker protocols
    2.8 clojure.pprint/print-table output compatible with Emacs Org mode
    2.9 clojure.string/replace and replace-first handle special characters more predictably
    2.10 Set and map constructor functions allow duplicates
    2.11 More functions preserve metadata
    2.12 New edn reader, improvements to *read-eval*
 3 Performance Enhancements
 4 Improved error messages
 5 Improved documentation strings
 6 Bug Fixes
 7 Binary Compatibility Notes

1 Deprecated and Removed Features

1.1 Clojure 1.5 reducers library requires Java 6 or later

The new reducers library (see below) requires Java 6 plus a ForkJoin library, or Java 7 or later. Clojure 1.5 can still be compiled and run with Java 5. The only limitations with Java 5 are that the new reducers library will not work, and building Clojure requires skipping the test suite (e.g. by using the command "ant jar").

2 New and Improved Features

2.1 Reducers

Reducers provide a set of high performance functions for working with collections. The actual fold/reduce algorithms are specified via the collection being reduced. This allows each collection to define the most efficient way to reduce its contents.

The implementation details of reducers are available at the Clojure blog and therefore won't be repeated in these change notes. However, as a summary:

  • There is a new namespace: clojure.core.reducers
  • It contains new versions of map, filter etc based upon transforming reducing functions - reducers
  • It contains a new function, fold, which is a parallel reduce+combine fold uses fork/join when working with (the existing!) Clojure vectors and maps
  • Your new parallel code has exactly the same shape as your existing seq-based code
  • The reducers are composable
  • Reducer implementations are primarily functional - no iterators
  • The model uses regular data structures, not 'parallel collections' or other OO malarkey
  • It's fast, and can become faster still
  • This is work-in-progress

Examples:

user=> (require '[clojure.core.reducers :as r])
user=> (reduce + (r/filter even? (r/map inc [1 1 1 2])))
;=> 6


;;red is a reducer awaiting a collection
user=> (def red (comp (r/filter even?) (r/map inc)))
user=> (reduce + (red [1 1 1 2]))
;=> 6

user=> (into #{} (r/filter even? (r/map inc [1 1 1 2])))
;=> #{2}

2.2 Reader Literals improved

  • CLJ-1034 "Conflicting data-reader mapping" should no longer be thrown where there really isn't a conflict. Until this patch, having data_readers.clj on the classpath twice would cause the above exception.

  • CLJ-927 Added *default-data-reader-fn* to clojure.core. When no data reader is found for a tag and *default-data-reader-fn*is non-nil, it will be called with two arguments, the tag and the value. If *default-data-reader-fn* is nil (the default), an exception will be thrown for the unknown tag.

2.3 clojure.core/set-agent-send-executor!, set-agent-send-off-executor!, and send-via

Added two new functions:

  • clojure.core/set-agent-send-executor!

    Allows the user to set the java.util.concurrent.Executor used when calling clojure.core/send. Defaults to a fixed thread pool of size: (numCores + 2)

  • clojure.core/set-agent-send-off-executor!

    Allows the user to set the java.util.concurrent.Executor used when calling clojure.core/send-off. Defaults to a cached thread pool.

  • clojure.core/send-via

    Like send, and send-off, except the first argument to this function is an executor to use when sending.

2.4 New threading macros

  • clojure.core/cond-> [expr & clauses]

    Takes an expression and a set of test/form pairs. Threads the expression (via ->) through each form for which the corresponding test expression (not threaded) is true.

Example:

user=> (cond-> 1
			   true inc
               false (* 42)
               (= 2 2) (* 3))
6

  • clojure.core/cond->> [expr & clauses]

    Takes an expression and a set of test/form pairs. Threads expr (via ->>) through each form for which the corresponding test expression (not threaded) is true.

Example:

user=> (def d [0 1 2 3])
#'user/d
user=> (cond->> d
			    true (map inc)
				(seq? d) (map dec)
				(= (count d) 4) (reduce +)) ;; no threading in the test expr
				                            ;; so d must be passed in explicitly
10
  • clojure.core/as-> [expr name & forms]

Binds name to expr, evaluates the first form in the lexical context of that binding, then binds name to that result, repeating for each successive form

Note: this form does not actually perform any threading. Instead it allows the user to assign a name and lexical context to a value created by a parent threading form.

Example:

user=> (-> 84
    	   (/ 4)
    	   (as-> twenty-one          ;; uses the value from ->
           		  (* 2 twenty-one)))  ;; no threading here
42
  • clojure.core/some-> [expr & forms]

When expr is not nil, threads it into the first form (via ->), and when that result is not nil, through the next etc.

Example:

user=> (defn die [x] (assert false))
#'user/die
user=> (-> 1 inc range next next next die)
AssertionError Assert failed: false  user/die (NO_SOURCE_FILE:65)
user=> (some-> 1 inc range next next next die)
nil

  • clojure.core/some->> [expr & forms]

    When expr is not nil, threads it into the first form (via ->>), and when that result is not nil, through the next etc.

    Same as some-> except the value is threaded as the last argument in each form.

2.5 Column metadata captured by reader

  • CLJ-960 Data read by the clojure reader is now tagged with :column in addition to :line.

2.6 gen-class improvements

  • CLJ-745 It is now possible to expose protected final methods via :exposes-methods in gen-class. This allows Clojure classes created via gen-class to access protected methods of its parent class.

Example:

(gen-class :name clojure.test_clojure.genclass.examples.ProtectedFinalTester
	       :extends java.lang.ClassLoader
    	   :main false
       	   :prefix "pf-"
       	   :exposes-methods {findSystemClass superFindSystemClass})
  • CLJ-948 It is now possible to annotate constructors via gen-class.

Example:

(gen-class :name foo.Bar
	       :extends clojure.lang.Box
    	   :constructors {^{Deprecated true} [Object] [Object]}
       	   :init init
       	   :prefix "foo")

2.7 Support added for marker protocols

  • CLJ-966 defprotocol no longer requires that at least one method be given in the definition of the protocol. This allows for marker protocols, whose sole reason of existence is to allow satisfies? to be true for a given type.

Example:

user=> (defprotocol P (hi [_]))
P
user=> (defprotocol M) ; marker protocol
M
user=> (deftype T [a] M P (hi [_] "hi there"))
user.T
user=> (satisfies? P (T. 1))
true
user=> (satisfies? M (T. 1))
true
user=> (hi (T. 1))
"hi there"
user=> (defprotocol M2 "marker for 2") ; marker protocol again
M2
user=> (extend-type T M2)
nil
user=> (satisfies? M2 (T. 1))
true

2.8 clojure.pprint/print-table output compatible with Emacs Org mode

For the convenience of those that use Emacs Org mode, clojure.pprint/print-table now prints tables in the form used by that mode. Emacs Org mode has features to make it easy to edit such tables, and even to do spreadsheet-like calculations on their contents. See the Org mode documentation on tables for details.

user=> (clojure.pprint/print-table [:name :initial-impression]
           [{:name "Rich" :initial-impression "rock star"}
            {:name "Andy" :initial-impression "engineer"}])
| :name | :initial-impression |
|-------+---------------------|
|  Rich |           rock star |
|  Andy |            engineer |

2.9 clojure.string/replace and replace-first handle special characters more predictably

clojure.string/replace and clojure.string/replace-first are now consistent in the way that they handle the replacement strings: all characters in the replacement strings are treated literally, including backslash and dollar sign characters.

user=> (require '[clojure.string :as s])

user=> (s/replace-first "munge.this" "." "$")
;=> "munge$this"

user=> (s/replace "/my/home/dir" #"/" (fn [s] "\\"))
;=> "\\my\\home\\dir"

There is one exception, which is described in the doc strings. If you call these functions with a regex to search for and a string as the replacement, then dollar sign and backslash characters in the replacement string are treated specially. Occurrences of $1 in the replacement string are replaced with the string that matched the first parenthesized subexpression of the regex, occurrences of $2 are replaced with the match of the second parenthesized subexpression, etc.

user=> (s/replace "x12, b4" #"([a-z]+)([0-9]+)" "$1 <- $2")
;=> "x <- 12, b <- 4"

Individual occurrences of $ or \ in the replacement string that you wish to be treated literally can be escaped by prefixing them with a \. If you wish your replacement string to be treated literally and its contents are unknown to you at compile time (or you don't wish to tarnish your constant string with lots of backslashes), you can use the new function clojure.string/re-quote-replacement to do the necessary escaping of special characters for you.

user=> (s/replace "x12, b4" #"([a-z]+)([0-9]+)"
                     (s/re-quote-replacement "$1 <- $2"))
;=> "$1 <- $2, $1 <- $2"

2.10 Set and map constructor functions allow duplicates

All of the functions that construct sets such as set and sorted-set allow duplicate elements to appear in their arguments, and they are documented to treat this case as if by repeated uses of conj.

Similarly, all map constructor functions such as hash-map, array-map, and sorted-map allow duplicate keys, and are documented to treat this case as if by repeated uses of assoc.

As before, literal sets, e.g. #{1 2 3}, do not allow duplicate elements, and while elements can be expressions evaluated at run time such as #{(inc x) (dec y)}, this leads to a check for duplicates at run time whenever the set needs to be constructed, throwing an exception if any duplicates are found.

Similarly, literal maps do not allow duplicate keys. New to Clojure 1.5 is a performance optimization: if all keys are compile time constants but one or more values are expressions requiring evaluation at run time, duplicate keys are checked for once at compile time only, not each time a map is constructed at run time.

  • CLJ-1065 Allow duplicate set elements and map keys for all set and map constructors

2.11 More functions preserve metadata

Most functions that take a collection and return a "modified" version of that collection preserve the metadata that was on the input collection, e.g. conj, assoc, dissoc, etc. One notable exception was into, which would return a collection with metadata nil for several common types of input collections.

Now the functions into, select-keys, clojure.set/project, and clojure.set/rename return collections with the same metadata as their input collections.

2.12 New edn reader, improvements to *read-eval*

The new clojure.edn namespace reads edn (http://edn-format.org) data, and should be used for reading data from untrusted sources.

Clojure's core read* functions can evaluate code, and should not be used to read data from untrusted sources. As of 1.5, *read-eval* supports a documented set of thread-local bindings, see the doc string for details.

*read-eval*'s default can be set to false by setting a system property:

-Dclojure.read.eval=false

3 Performance and Memory Enhancements

  • CLJ-988 Multimethod tables are now protected by a read/write lock instead of a synchronized method. This should result in a performance boost for multithreaded code using multimethods.
  • CLJ-1061 when-first now evaluates its expression only once.
  • CLJ-1084 PersistentVector$ChunkedSeq now implements Counted interface, to avoid some cases where vector elements were being counted by iterating over their elements.
  • CLJ-867 Records with same fields and field values, but different types, now usually hash to different values.
  • CLJ-1000 Cache hasheq() for seqs, sets, vectors, maps and queues
  • (no ticket) array-map perf tweaks
  • CLJ-1111 Allows loop to evaluate to primitive values
  • (no ticket) Move loop locals into same clearing context as loop body

4 Improved error messages

  • CLJ-103 Improved if-let error message when form has a improperly defined body.
  • CLJ-897 Don't use destructuring in defrecord/deftype arglists to get a slightly better error message when forgetting to specify the fields vector
  • CLJ-788 Add source and line members and getters to CompilerException
  • CLJ-157 Better error messages for syntax errors w/ defn and fn
  • CLJ-940 Passing a non-sequence to refer :only results in uninformative exception
  • CLJ-1052 assoc now throws an exception if the last key argument is missing a value.

5 Improved documentation strings

  • CLJ-893 Document that vec will alias Java arrays
  • CLJ-892 Clarify doc strings of sort and sort-by: they will modify Java array arguments
  • CLJ-1019 ns-resolve doc has a typo
  • CLJ-1038 Docstring for deliver doesn't match behavior
  • CLJ-1055 "be come" should be "become"
  • CLJ-917 clojure.core/definterface is not included in the API docs
  • (no ticket) clojure.core/read, read-string, and read-eval all have more extensive documentation.

6 Bug Fixes

  • CLJ-962 Vectors returned by subvec allow access at negative indices
  • CLJ-952 bigdec does not properly convert a clojure.lang.BigInt
  • CLJ-975 inconsistent destructuring behaviour when using nested maps
  • CLJ-954 TAP support in clojure.test.tap Needs Updating
  • CLJ-881 exception when cl-format is given some ~f directive/value combinations
  • CLJ-763 Do not check for duplicates in destructuring map creation
  • CLJ-667 Allow loops fully nested in catch/finally
  • CLJ-768 cl-format bug in ~f formatting
  • CLJ-844 NPE calling keyword on map from bean
  • CLJ-934 disj! Throws exception when attempting to remove multiple items in one call
  • CLJ-943 When load-lib fails, a namespace is still created
  • CLJ-981 clojure.set/rename-keys deletes keys when there's a collision
  • CLJ-961 with-redefs loses a Var's root binding if the Var is thread-bound
  • CLJ-1032 seque leaks threads from the send-off pool
  • CLJ-1041 reduce-kv on sorted maps should stop on seeing a Reduced value
  • CLJ-1011 clojure.data/diff should cope with null and false values in maps
  • CLJ-977 (int \a) returns a value, (long \a) throws an exception
  • CLJ-964 test-clojure/rt.clj has undeclared dependency on clojure.set
  • CLJ-923 Reading ratios prefixed by + is not working
  • CLJ-1012 partial function should also accept 1 arg (just f)
  • CLJ-932 contains? Should throw exception on non-keyed collections
  • CLJ-730 Create test suite for functional fns (e.g. juxt, comp, partial, etc.)
  • CLJ-757 Empty transient maps/sets return wrong value for .contains
  • CLJ-828 clojure.core/bases returns a cons when passed a class and a Java array when passed an interface
  • CLJ-1062 CLJ-940 breaks compilation of namespaces that don't have any public functions
  • CLJ-1070 PersistentQueue's hash function does not match its equality
  • CLJ-987 pprint doesn't flush the underlying stream
  • CLJ-963 Support pretty printing namespace declarations under code-dispatch
  • CLJ-902 doc macro broken for namespaces
  • CLJ-909 Make LineNumberingPushbackReader's buffer size configurable
  • CLJ-910 Allow for type-hinting the method receiver in memfn
  • CLJ-1048 add test.generative to Clojure's tests
  • CLJ-1071 ExceptionInfo does no abstraction
  • CLJ-1085 clojure.main/repl unconditionally refers REPL utilities into *ns*
  • (no ticket) Rich Hickey fix: syntax-quote was walking records, returning maps
  • CLJ-1116 More REPL-friendly 'ns macro
  • (no ticket) Rich Hickey fix: deref any j.u.c.Future
  • CLJ-1092 New function re-quote-replacement has incorrect :added metadata
  • CLJ-1098 Implement IKVReduce and CollFold for nil
  • (no ticket) Rich Hickey fix: impose once semantics on fabricated closures for e.g. loops
  • CLJ-1140 Restore {:as x} destructuring for empty lists
  • CLJ-1150 Make some PersistentVector's and APersistentVector.SubVector's internals public
  • (no ticket) Rich Hickey fix: use non-loading classForName
  • CLJ-1106 Fixing set equality

7 Binary Compatibility Notes

  • public static inner class LispReader.ReaderException(int line, Throwable cause) Constructor changed to ReaderException(int line, int column, Throwable cause)
  • public Object clojure.lang.Agent.dispatch(IFn fn, ISeq args, boolean solo) Replaced with dispatch(IFn fn, ISeq args, Executor exec)

Changes to Clojure in Version 1.4

CONTENTS

 1 Deprecated and Removed Features
    1.1 Fields that Start With a Dash Can No Longer Be Accessed Using Dot Syntax
 2 New/Improved Features
    2.1 Reader Literals
    2.2 clojure.core/mapv
    2.3 clojure.core/filterv
    2.4 clojure.core/ex-info and clojure.core/ex-data
    2.5 clojure.core/reduce-kv
    2.6 clojure.core/contains? Improved
    2.7 clojure.core/min and clojure.core/max prefer NaN
    2.8 clojure.java.io/as-file and clojure.java.io/as-url Handle URL-Escaping Better
    2.9 New Dot Syntax for Record and Type Field Access
    2.10 Record Factory Methods Available Inside defrecord
    2.11 assert-args Displays Namespace and Line Number on Errors
    2.12 File and Line Number Added to Earmuff Dynamic Warning
    2.13 require Can Take a :refer Option
    2.14 *compiler-options* Var
    2.15 Improved Reporting of Invalid Characters in Unicode String Literals
    2.16 clojure.core/hash No Longer Relies on .hashCode
    2.17 Java 7 Documentation
    2.18 loadLibrary Loads Library Using System ClassLoader
    2.19 Java int is boxed as java.lang.Integer
 3 Performance Enhancements
 4 Bug Fixes

1 Deprecated and Removed Features

1.1 Record and Type Fields that Start With a Dash Can No Longer Be Accessed Using Dot Syntax

Clojure 1.4 introduces a field accessor syntax for the dot special form that aligns Clojure field lookup syntax with ClojureScript's.

For example, in Clojure 1.3, one can declare a record with a field starting with dash and access it like this:

(defrecord Bar [-a]) ;=> user.Bar
(.-a (Bar. 10)) ;=> 10

In 1.4, the above code results in IllegalArgumentException No matching field found: a for class user.Bar

However, the field may still be accessed as a keyword:

(:-a (Bar. 10)) ;=> 10

2 New and Improved Features

2.1 Reader Literals

Clojure 1.4 supports reader literals, which are data structures tagged by a symbol to denote how they will be read.

When Clojure starts, it searches for files named data_readers.clj at the root of the classpath. Each such file must contain a Clojure map of symbols, like this:

{foo/bar my.project.foo/bar
 foo/baz my.project/baz}

The key in each pair is a tag that will be recognized by the Clojure reader. The value in the pair is the fully-qualified name of a Var which will be invoked by the reader to parse the form following the tag. For example, given the data_readers.clj file above, the Clojure reader would parse this form:

#foo/bar [1 2 3]

by invoking the Var #'my.project.foo/bar on the vector [1 2 3]. The data reader function is invoked on the form AFTER it has been read as a normal Clojure data structure by the reader.

Reader tags without namespace qualifiers are reserved for Clojure. Default reader tags are defined in clojure.core/default-data-readers but may be overridden in data_readers.clj or by rebinding *data-readers*.

2.1.1 Instant Literals

Clojure supports literals for instants in the form #inst "yyyy-mm-ddThh:mm:ss.fff+hh:mm". These literals are parsed as java.util.Dates by default. They can be parsed as java.util.Calendars or java.util.Timestamps by binding *data-readers* to use clojure.instant/read-instant-calendar or clojure.instant/read-instant-timestamp.

(def instant "#inst \"@2010-11-12T13:14:15.666\"")

; Instants are read as java.util.Date by default
(= java.util.Date (class (read-string instant)))
;=> true

; Instants can be read as java.util.Calendar or java.util.Timestamp

(binding [*data-readers* {'inst read-instant-calendar}]
  (= java.util.Calendar (class (read-string instant))))
;=> true

(binding [*data-readers* {'inst read-instant-timestamp}]
  (= java.util.Timestamp (class (read-string instant))))
;=> true

2.1.2 UUID Literals

Clojure supports literals for UUIDs in the form #uuid "uuid-string". These literals are parsed as java.util.UUIDs.

2.2 clojure.core/mapv

mapv takes a function f and one or more collections and returns a vector consisting of the result of applying f to the set of first items of each collection, followed by applying f to the set of second items in each collection, until any one of the collections is exhausted. Any remaining items in other collections are ignored. f should accept a number of arguments equal to the number of collections.

(= [1 2 3] (mapv + [1 2 3]))
;=> true

(= [2 3 4] (mapv + [1 2 3] (repeat 1)))
;=> true

2.3 clojure.core/filterv

filterv takes a predicate pred and a collection and returns a vector of the items in the collection for which (pred item) returns true. pred must be free of side-effects.

(= [] (filterv even? [1 3 5]))
;=> true

(= [2 4] (filterv even? [1 2 3 4 5]))
;=> true

2.4 clojure.core/ex-info and clojure.core/ex-data

ex-info creates an instance of ExceptionInfo. ExceptionInfo is a RuntimeException subclass that takes a string msg and a map of data.

(ex-info "Invalid use of robots" {:robots false})
;=> #<ExceptionInfo clojure.lang.ExceptionInfo: Invalid use of robots {:robots false}>

ex-data is called with an exception and will retrieve that map of data if the exception is an instance of ExceptionInfo.

(ex-data (ex-info "Invalid use of robots" {:robots false}))
;=> {:robots false}

2.5 clojure.core/reduce-kv

reduce-kv reduces an associative collection. It takes a function f, an initial value init and an associative collection coll. f should be a function of 3 arguments. Returns the result of applying f to init, the first key and the first value in coll, then applying f to that result and the 2nd key and value, etc. If coll contains no entries, returns init and f is not called. Note that reduce-kv is supported on vectors, where the keys will be the ordinals.

(reduce-kv str "Hello " {:w \o :r \l :d \!})
;=> "Hello :rl:d!:wo"
(reduce-kv str "Hello " [\w \o \r \l \d \!])
;=> "Hello 0w1o2r3l4d5!"

2.6 clojure.core/contains? Improved

contains? now works with java.util.Set.

2.7 clojure.core/min and clojure.core/max prefer NaN

min and max now give preference to returning NaN if either of their arguments is NaN.

2.8 clojure.java.io/as-file and clojure.java.io/as-url Handle URL-Escaping Better

as-file and as-url now handle URL-escaping in both directions.

2.9 New Dot Syntax for Record and Type Field Access

Clojure 1.4 introduces a field accessor syntax for the dot special form that aligns Clojure field lookup syntax with ClojureScript's.

In 1.4, to declare a record type and access its property x, one can write:

(defrecord Foo [x]) ;=> user.Foo
(.-x (Foo. 10)) ;=> 10

This addition makes it easier to write code that will run as expected in both Clojure and ClojureScript.

2.10 Record Factory Methods Available Inside defrecord

Prior to 1.4, you could not use the factory functions (->RecordClass and map->RecordClass) to construct a new record from inside a defrecord definition.

The following example did not work prior to 1.4, but is now valid. This example makes use of ->Mean which would have not yet been available.

(defrecord Mean [last-winner]
  Player
  (choose [_] (if last-winner last-winner (random-choice)))
  (update-strategy [_ me you] (->Mean (when (iwon? me you) me))))

2.11 assert-args Displays Namespace and Line Number on Errors

assert-args now uses &form to report the namespace and line number where macro syntax errors occur.

2.12 File and Line Number Added to Earmuff Dynamic Warning

When a variable is defined using earmuffs but is not declared dynamic, Clojure emits a warning. That warning now includes the file and line number.

2.13 require Can Take a :refer Option

require can now take a :refer option. :refer takes a list of symbols to refer from the namespace or :all to bring in all public vars.

2.14 *compiler-options* Var

The dynamic var *compiler-options* contains a map of options to send to the Clojure compiler.

Supported options:

  • :elide-meta: Have certain metadata elided during compilation. This should be set to a collection of keywords.
  • :disable-locals-clearing: Set to true to disable clearing. Useful for using a debugger.

The main function of the Clojure compiler sets the *compiler-options* from properties prefixed by clojure.compiler, e.g.

java -Dclojure.compiler.elide-meta='[:doc :file :line]'

2.15 Improved Reporting of Invalid Characters in Unicode String Literals

When the reader finds an invalid character in a Unicode string literal, it now reports the character instead of its numerical representation.

2.16 clojure.core/hash No Longer Relies on .hashCode

hash no longer directly uses .hashCode() to return the hash of a Clojure data structure. It calls clojure.lang.Util.hasheq, which has its own implementation for Integer, Short, Byte, and Clojure collections. This ensures that the hash code returned is consistent with =.

2.17 Java 7 Documentation

*core-java-api* will now return the URL for the Java 7 Javadoc when you are running Java 7.

2.18 loadLibrary Loads Library Using System ClassLoader

A static method, loadLibrary, was added to clojure.lang.RT to load a library using the system ClassLoader instead of Clojure's class loader.

2.19 Java int is Boxed As java.lang.Integer

Java ints are now boxed as java.lang.Integers. See the discussion on clojure-dev for more information.

3 Performance Enhancements

  • (= char char) is now optimized
  • equiv is inlined in variadic =
  • toString cached on keywords and symbols

4 Bug Fixes

  • CLJ-829 Transient hashmaps mishandle hash collisions
  • CLJ-773 Macros that are expanded away still have their vars referenced in the emitted byte code
  • CLJ-837 java.lang.VerifyError when compiling deftype or defrecord with argument name starting with double underscore characters
  • CLJ-369 Check for invalid interface method names
  • CLJ-845 Unexpected interaction between protocol extension and namespaced method keyword/symbols
    • Ignoring namespace portion of symbols used to name methods in extend-type and extend-protocol
  • CLJ-852 IllegalArgumentException thrown when defining a var whose value is calculated with a primitive fn
  • CLJ-855 catch receives a RuntimeException rather than the expected checked exception
  • CLJ-876 #^:dynamic vars declared in a nested form are not immediately dynamic
  • CLJ-886 java.io/do-copy can garble multibyte characters
  • CLJ-895 Collection.toArray implementations do not conform to Java API docs
    • obey contract for toArray return type
  • CLJ-898 Agent sends consume heap
    • Only capture a shallow copy of the current Frame in binding-conveyor-fn, so that sends in agent actions don't build infinite Frame stacks
  • CLJ-928 Instant literal for Date and Timestamp should print in UTC
  • CLJ-931 Syntactically broken clojure.test/are tests succeed
  • CLJ-933 Compiler warning on clojure.test-clojure.require-scratch

Changes to Clojure in Version 1.3

CONTENTS

 1 Deprecated and Removed Features
    1.1 Earmuffed Vars are No Longer Automatically Considered Dynamic
    1.2 ISeq No Longer Inherits from Sequential
    1.3 Removed Bit Operation Support for Boxed Numbers
    1.4 Ancillary Namespaces No Longer Auto-Load on Startup
    1.5 Replicate Deprecated
 2 New/Improved Features
    2.1 Enhanced Primitive Support
    2.2 defrecord and deftype Improvements
    2.3 Better Exception Reporting
    2.4 clojure.reflect/reflect
    2.5 clojure.data/diff
    2.6 clojure.core/every-pred and clojure.core/some-fn Combinators
    2.7 clojure.core/realized?
    2.8 clojure.core/with-redefs-fn & with-redefs
    2.9 clojure.core/find-keyword
    2.10 clojure.repl/pst
    2.11 clojure.pprint/print-table
    2.12 pprint respects *print-length*
    2.13 compilation and deployment via Maven
    2.14 internal keyword map uses weak refs
    2.15 ^:const defs
    2.16 Message Bearing Assert
    2.17 Error Checking for defmulti Options
    2.18 Removed Checked Exceptions
    2.19 vector-of Takes Multiple Arguments
    2.20 deref with timeout
    2.21 Walk Support for sorted-by Collections
    2.22 string.join Enhanced to Work with Sets
    2.23 clojure.test-helper
    2.24 Newline outputs platform-specific newline sequence
    2.25 init-proxy and update-proxy return proxy
    2.26 doc & find-doc moved to REPL
    2.27 clojure.java.shell/sh accepts as input anything that clojure.java.io/copy does
    2.28 InterruptedHandler Promoted to clojure.repl
    2.29 Add support for running -main namespaces from clojure.main
    2.30 Set thread names on agent thread pools
    2.31 Add docstring support to def
    2.32 Comp function returns identity when called with zero arity
    2.33 Type hints can be applied to arg vectors
    2.34 Binding Conveyance
 3 Performance Enhancements
 4 Bug Fixes
 5 Modular Contrib

1 Deprecated and Removed Features

1.1 Earmuffed Vars Are No Longer Automatically Considered Dynamic.

(def *fred*)
=> Warning: *fred* not declared dynamic and thus is not dynamically rebindable, but its name suggests otherwise. Please either indicate ^:dynamic ** or change the name.

1.2 ISeq No Longer Inherits From Sequential

This allows ISeq implementers to be in the map or set equality partition.

1.3 Removed Bit Operation Support for Boxed Numbers

Bit Operations map directly to primitive operations

1.4 Ancillary Namespaces No Longer Auto-Load on Startup

The following namespaces are no longer loaded on startup: clojure.set, clojure.xml, clojure.zip

1.5 Replicate Deprecated

Use repeat instead.

2 New/Improved Features

2.1 Enhanced Primitive Support

Full details here:

2.2 defrecord and deftype Improvements

Details here: Defrecord Improvements

2.3 Better Exception Reporting

Details here: Error Handling

Additionally:

Better error messages:

  • When calling macros with arity
  • For Invalid Map Literals
  • For alias function if using unknown namespace
  • In the REPL
  • Add "starting at " to EOF while reading exceptions
  • Better compilation error reporting

2.4 clojure.reflect/reflect

Full details here: Reflection API

2.5 clojure.data/diff

Recursively compares a and b, returning a tuple of [things-only-in-a things-only-in-b things-in-both]

(diff {:a 1 :b 2} {:a 1 :b 22 :c 3})
=> ({:b 2} {:c 3, :b 22} {:a 1})

2.6 clojure.core/every-pred and clojure.core/some-fn Combinators

every-pred takes a set of predicates and returns a function f that returns true if all of its composing predicates return a logical true value against all of its arguments, else it returns false.

((every-pred even?) 2 4 6)
=> true

((every-pred even?) 2 4 5)
=>false

some-fn takes a set of predicates and returns a function f that returns the first logical true value returned by one of its composing predicates against any of its arguments, else it returns logical false.

((some-fn even?) 2 4 5)
=> true
((some-fn odd?) 2 4 6)
=> false

2.7 clojure.core/realized?

Returns true if a value has been produced for a promise, delay, future or lazy sequence.

(let [x (range 5)]
  (println (realized? x))
  (first x)
  (println (realized? x)))
=> false
=> true

2.8 clojure.core/with-redefs-fn & clojure.core/with-redefs

with-redefs-fn temporarily redefines Vars during a call to func. with-redefs temporarily redefines Vars while executing the body.

(with-redefs [nil? :temp] (println nil?))
=> :temp

2.9 clojure.core/find-keyword

Returns a Keyword with the given namespace and name if one already exists.

(find-keyword "def")
=> :def
(find-keyword "fred")
=> nil

2.10 clojure.repl/pst

Prints a stack trace of the exception

(pst (IllegalArgumentException.))

IllegalArgumentException
    user/eval27 (NO_SOURCE_FILE:18)
    clojure.lang.Compiler.eval (Compiler.java:6355)
    clojure.lang.Compiler.eval (Compiler.java:6322)
    clojure.core/eval (core.clj:2699)
    clojure.main/repl/read-eval-print--5906 (main.clj:244)
    clojure.main/repl/fn--5911 (main.clj:265)
    clojure.main/repl (main.clj:265)
    clojure.main/repl-opt (main.clj:331)
    clojure.main/main (main.clj:427)
    clojure.lang.Var.invoke (Var.java:397)
    clojure.lang.Var.applyTo (Var.java:518)
    clojure.main.main (main.java:37)

2.11 clojure.pprint/print-table

Prints a collection of maps in a textual table.

(print-table [:fred :barney]
             [{:fred "ethel"}
              {:fred "wilma" :barney "betty"}])

===============
:fred | :barney
===============
ethel |
wilma | betty
===============

2.12 pprint respects *print-length*

Assigning *print-length* now affects output of pprint

2.13 compilation and deployment via Maven

See the following pages for more information:

2.14 internal keyword map uses weak refs

2.15 ^:const defs

^:const lets you name primitive values with speedier reference.

(def constants
 {:pi 3.14
  :e 2.71})

(def ^:const pi (:pi constants))
(def ^:const e (:e constants))

The overhead of looking up :e and :pi in the map happens at compile time, as (:pi constants) and (:e constants) are evaluated when their parent def forms are evaluated.

2.16 Message Bearing Assert

Assert can take a second argument which will be printed when the assert fails

(assert (= 1 2) "1 is not equal to 2")
=> AssertionError Assert failed: 1 is not equal to 2

2.17 Error Checking for defmulti Options

defmulti will check to verify that its options are valid. For example, the following code will throw an exception:

(defmulti fred :ethel :lucy :ricky)
=> IllegalArgumentException

2.18 Removed Checked Exceptions

Clojure does not throw checked exceptions

2.19 vector-of Takes Multiple Args

vector-of takes multiple args used to populate the array

(vector-of :int 1 2 3)
=> [1 2 3]

2.20 deref with timeout

deref now takes a timeout option - when given with a blocking reference, will return the timeout-val if the timeout (in milliseconds) is reached before value is available.

(deref (promise) 10 :ethel)
=> :ethel

2.21 Walk Support for sorted-by Collections

Walk modified to work on sorted-by collections

let [x (sorted-set-by > 1 2 3)] (walk inc reverse x))
=> (2 3 4)

2.22 string.join Enhanced to Work with Sets

Just like join works on other collections

(join " and " #{:fred :ethel :lucy})
=> ":lucy and :fred and :ethel"

2.23 clojure.test-helper

All test helpers moved into clojure.test-helper

2.24 Newline outputs platform-specific newline sequence

Newline sequence is output as \r\n on Windows now.

2.25 init-proxy and update-proxy return proxy

Now you can chain calls on the proxy

2.26 doc & find-doc moved to REPL

Adds special form docs to the REPL

2.27 clojure.java.shell/sh accepts as input anything that clojure.java.io/copy does

This adds InputStream, Reader, File, byte[] to the list of inputs for clojure.java.shell/sh

2.28 Interrupt Handler Promoted to clojure.repl

Promoting this library eliminates the need for a dependency on old contrib.

2.29 Add support for running -main namespaces from clojure.main

This patch allows clojure.main to accept an argument pointing to a namespace to look for a -main function in. This allows users to write -main functions that will work the same whether the code is AOT-compiled for use in an executable jar or just run from source.

2.30 Set thread names on agent thread pools

It's a best practice to name the threads in an executor thread pool with a custom ThreadFactory so that the purpose of these threads is clear in thread dumps and other runtime operational tools.

Patch causes thread names like:

clojure-agent-send-pool-%d     (should be fixed # of threads)
clojure-agent-send-off-pool-%d (will be added and removed over time)

2.31 Add docstring support to def

A def can now have a docstring between name and value.

(def foo "a foo" :foo)

2.32 Comp function returns identity when called with zero arity

(= (comp) identity)
=> true

2.33 Type hints can be applied to arg vectors

You can hint different arities separately:

(defn hinted
  (^String [])
  (^Integer [a])
  (^java.util.List [a & args]))

This is preferred over hinting the function name. Hinting the function name is still allowed for backward compatibility, but will likely be deprecated in a future release.

2.34 Binding Conveyance

Clojure APIs that pass work off to other threads (e.g. send, send-off, pmap, future) now convey the dynamic bindings of the calling thread:

(def ^:dynamic *num* 1)
(binding [*num* 2] (future (println *num*)))
;; prints "2", not "1"

3 Performance Enhancements

  • Code path for using vars is now much faster for the common case
  • Improved startup time
  • Fix performance on some numeric overloads See CLJ-380 for more information
  • Promises are lock free
  • Functions only get metadata support code when metadata explicitly supplied
  • definterface/gen-interface accepts array type hints
  • inline nil?
  • inline bit-functions & math ops
  • inline n-ary min & max
  • PersistentQueue count is now O(1)
  • Intrinsics: unchecked math operators now emit bytecodes directly where possible

4 Bug Fixes

Complete list of Tickets for 1.3 Release.

  • CLJ-8 detect and report cyclic load dependencies

    • Patch restore detection of cyclic load dependencies

  • CLJ-31 compiler now correctly rejects attempts to recur across try (fn [x] (try (recur 1))) => CompilerException

  • CLJ-286 *out* being used as java.io.PrintWriter

    • Patch fixes using Writer instead of PrintWriter
    • fix clojure.main to not assume that err is a PrintWriter

  • CLJ-292 LazySeq.sval() nests RuntimeExceptions

    • Patch causes only the original RuntimeException to be thrown

  • CLJ-390 sends from agent error-handlers should be allowed

    • Patch allows agent error-handler to send successfully

  • CLJ-426 case should handle hash collision

    • There were situations where a hash collision would occur with case and an exception would be thrown. See discussion for more details

  • CLJ-430 clojure.java.io URL Coercion throws java.lang.ClassCastException

    • Patch correct exception to be thrown

  • CLJ-432 deftype does not work if containing ns contains dashes

    • Patch munges namespaces with dashes properly

  • CLJ-433 munge should not munge $ (which isJavaIdentifierPart), should munge ' (which is not)

  • CLJ-435 stackoverflow exception in printing meta with :type

    • Patch fixes exception being thrown on certain type metadata (with-meta {:value 2} {:type Object}) => No message. [Thrown class java.lang.StackOverflowError]

  • CLJ-437 Bugs in clojure.set/subset? and superset? for sets with false/nil elements

    • Patch fixes failing on subset? and superset? for sets with false/nil elements

  • CLJ-439 Automatic type translation from Integer to Long

    • Patch fixes increase coercion from Integer to Long

  • CLJ-444 Infinite recursion in Keyword.intern leads to stack overflow

    • No more infinite recursion with patch

  • CLJ-673 use system class loader when base loader is null

    • facilitates placing Clojure on bootclasspath

  • CLJ-678 into-array should work with all primitive types

  • CLJ-680 printing promises should not block

    • Patch allows printing of promises without blocking

  • CLJ-682 cl-format: ~w throws an exception when not wrapped in a pretty-writer

    • Patch fixes the following bug in cl-format with ~w:

  • CLJ-693 VerifyError with symbol metadata, macros, and defrecord

  • CLJ-702 case gives NPE when used with nil

    • Patch allows nil to be used with case

  • CLJ-734 starting scope of let bindings seems incorrect from jdi perspective

    • Patch fixes local variables table to have the correct code index for let bindings.

  • CLJ-739 version.properties file is not closed

    • Patch properly closes version.properties file

  • CLJ-751 cl-format: ~( throws an exception with an empty string

    • Patch fixes the following bug in cl-format when format is nil (cl-format nil "~:(~a~)" "") => NullPointerException

  • CLJ-780 race condition in reference cache on Java 5

    • Map.Entry instances can have null values prior to Java 6. This patch provides a workaround.

  • floats were being boxed as Doubles, now they are boxed as Floats

  • several "holding onto head" fixes

    • Stop top-level defs from hanging onto the head of an expression that uses a lazy seq
    • Stop multimethods from holding onto heads of their arguments

5 Modular Contrib

In 1.3, the monolithic clojure-contrib.jar has been replaced by a modular system of contrib libraries, so that production systems can include only the code they actually need. This also allows individual contribs to have their own release cycles. Many contribs have moved forward by several point versions already. Documentation for updating applications to use the new contrib libraries is at http://dev.clojure.org/display/design/Where+Did+Clojure.Contrib+Go

Important Note: Many of the new modular contribs are compatible with both 1.2 and 1.3. This offers an incremental migration path: First, upgrade your contrib libraries while holding Clojure at 1.2, Then, in a separate step, upgrade to Clojure 1.3.

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