time-literals

A Clojure(Script) library which provides tagged literals for java.time objects, which on the jvm is objects from the java.time platform library and in Javascript is a java.time clone, called 'js-joda' .

This enables copying and pasting these objects within the REPL, conveying these objects across process boundaries & etc.

This talk provides some more background.

Note : To use this from Clojurescript, you must have an as yet unreleased version e.g. :

clj -Sdeps '{:deps {org.clojure/clojurescript {:git/url "https://github.com/clojure/clojurescript.git" :git/sha "f3e0bb503333bb53c4312d4bc19aa24505185667" } com.widdindustries/time-literals {:mvn/version "0.1.6"} }}' -m cljs.main  -re node  --repl 

Related Libraries

cljc.java-time is a one for one mapping of the classes and methods from java.time into a Clojure(Script) library

The tick library is an intuitive Clojure(Script) library for dealing with time, intended as a replacement for clj-time. It bundles this library and enables time-literals printing by default.

Usage

Lein/Boot/Deps

The library includes the magic file data_readers.cljc which Clojure and the Clojurescript compilers() will look for.

In order to modify the printer to print these literals, run:

(time-literals.read-write/print-time-literals-clj!)

(time-literals.read-write/print-time-literals-cljs!)

Example literals:

#time/month "JUNE"
#time/period "P1D"
#time/date "2039-01-01"
#time/date-time "2018-07-25T08:08:44.026"
#time/zoned-date-time "2018-07-25T08:09:11.227+01:00[Europe/London]"
#time/offset-date-time "2018-07-25T08:11:54.453+01:00"
#time/instant "2018-07-25T07:10:05.861Z"
#time/time "08:12:13.366"
#time/duration "PT1S"
#time/year "3030"
#time/year-month "3030-01"
#time/zone "Europe/London"
#time/day-of-week "TUESDAY"

ClojureScript

For example, in a Clojure repl:

  
 ;In a cljs repl
 (require '[java.time])  
 (println #time/duration "PT1S")
 ; => #object[Duration PT1S]
 ; Now, include printing and edn reading
 (require '[time-literals.read-write])
 (time-literals.read-write/print-time-literals-cljs!)
 (println #time/duration "PT1S")
 ; => #time/duration "PT1S"   
      

Self-hosted Cljs

TODO

Clojure

As with any non-core tagged literal, the tag reader functions referred to from a data_readers file must be loaded before the forms can be read.

(require '[time-literals.read-write]) ;; For printing/writing
(time-literals.read-write/print-time-literals-clj!)
(println #time/duration "PT1S")

Reading and Writing edn

(require '[time-literals.read-write])
(time-literals.read-write/print-time-literals-clj!)

Printing will now automatically change, for example re run the println above

Read edn like this:

(clojure.edn/read-string {:readers time-literals.read-write/tags} "#time/date \"2011-01-01\"")

Alternatives

If you only need Instant from java.time/jsr-310, you could just rebind the tag readers and printer fns for #inst. Note however that Clojure's inst format is based on RFC3339 and so is actually closer to the default format for java.time.OffsetDateTime (for example to read an inst tag, OffsetDateTime/parse will work ok, but Instant/parse will not). But... I think in most use cases Instant is preferred over OffsetDateTime as a representation of an absolute point in time. Rebinding inst reader and printer might also lead to problems where a programmer needs to work with both java.util.Date (or js/Date) and java.time.Instant objects - for example if using Datomic - it only works with java.util.Date objects.

There is a similar library, java-time-literals but this currently only works on the jvm, and also doesn't provide a way to read edn with the literals (via clojure.edn/read-string or cljs.reader). The naming of tags in this library (time-literals) follows the tick convention, for example #time/date for LocalDate, instead of #time/ld as in java-time-literals.

Why use 'time' as namespace?

TL;DR it is sufficiently ambiguous.

This library reads/writes java.time objects. It would be feasible to use the same set of tags with a different time library, either on the jvm or other elsewhere. If the namespace were 'jsr310' or 'java.time' that would be too implementaion specific.

A set of literals for the ISO-8601 specification would probably be the ideal for date interchange, with literals such as `#iso8601/ordinal-date"1981-095"``

However, although the Java.time domain overlaps significantly with concepts in ISO-8601, there are differences. For example, the ISO 'Duration' is roughly a combination of java.time.Duration and java.time.Period, and the IANA time zone names (such are you see in the literal representation of ZonedDateTime) are not part of ISO.

License

Copyright © 2021 Widd Industries

Distributed under the MIT License