Concise Data Format (CDF)

CDF is a very basic data serialization format implemented in a few hundred lines. It was designed with the following goals in mind:

1. Concise, readable, dev friendly
2. Small code footprint (doesn’t bloat client builds)
3. Suitable for embedding in HTML attributes

The result is a format somewhat akin to EDN… but also quite different.

The ‘top level’ of a CDF string is treated specially. If it’s empty, it's parsed as an empty string. If it starts with a digit or +/- then it’s parsed as a number. If it matches one of the following exactly, then it’s parsed accordingly:

• _ — parsed a nil
• true — parsed as true
• false — parsed as false

If it begins with one of the following, then it’s parsed accordingly:

• : — parsed as keyword
• [ — parsed as vector
• { — parsed as map
• ( — parsed as operation
• ` — parsed as a string, any number of sequential ticks can be used

Otherwise, the full top-level string is ‘parsed’ as itself… a string. Note that empty strings can't be written as ``, since that would just open a string that must be closed with two ticks. There's no need for any 'syntax' for empty strings at the top level... just use an empty string.

At an inner level (nested in a map, vector, or operation) the syntax is more formal. Numbers, keywords, maps, and vectors look as you’d expect. Strings are nested in between back-ticks. Operations look like (operator ...args) (these are customizable).

Some special values exist:

• E — empty string
• Inf+ — positive infinity
• Inf- — negative infinity
• NaN — not a number
• T — true
• F — false
• _ — nil

That’s it. That's the format.

Use zero.extras.cdf/read-str to parse a CDF string. An :operators option can be passed to specify custom operators. By default the reader supports operators matching the act, bnd, and << functions from zero.core, as well as a set for sets and inst for dates.

Use zero.extras.cdf/write-str to serialize to a CDF string. If a :mapper option is given, the provided function will be called on each value before it’s serialized; allowing for custom conversions. Lists with a symbol as the first value will be serialized as operations. The default mapper handles actions, bindings, injections, sets, and dates.