jsond

8.12

jsond🔗ℹ

D. Ben Knoble

package: jsond

This package provides a convienient format to embed JSON data in racket programs by making the JSON data (surprise!) racket programs.

1 Quick Start🔗ℹ

Suppose, for example, we had some JSON data consisting of a list of albums and singles.

["Cycles", "Flatspin", "Long Way to Climb"]

We also have a map of user favorites (each value is an index in the albums array).

{

"Jonathan Gordon": 0,

"Brad Rubinstein": 2,

"Paul Willmott": 1,

"Jason Hall": 0,

"Adam Rich": 1

}

Normally, we would need to require the json library and use read-json to read these data files. With jsond, however, we can make the files into a program:

#lang jsond

#:name albums
["Cycles", "Flatspin", "Long Way to Climb"]

#:name favorites
{
    "Jonathan Gordon": 0,
    "Brad Rubinstein": 2,
    "Paul Willmott": 1,
    "Jason Hall": 0,
    "Adam Rich": 1
}

If we put this in a file lisp.rkt, we suddenly have a program!

Examples:

> (require "lisp.rkt")
> albums
'("Cycles" "Flatspin" "Long Way to Climb")
> favorites
'#hasheq((|Adam Rich| . 1)
         (|Brad Rubinstein| . 2)
         (|Jason Hall| . 0)
         (|Jonathan Gordon| . 0)
         (|Paul Willmott| . 1))
> (for/hash ([(member fav-id) (in-hash favorites)])
    (values member (list-ref albums fav-id)))
'#hash((|Adam Rich| . "Flatspin")
       (|Brad Rubinstein| . "Long Way to Climb")
       (|Jason Hall| . "Cycles")
       (|Jonathan Gordon| . "Cycles")
       (|Paul Willmott| . "Flatspin"))

The program can also be run to recover the original JSON. The following racket code is equivalent to running a command-line

# racket lisp.rkt

Example:

> (require (submod "lisp.rkt" main))
{"albums":["Cycles","Flatspin","Long Way to Climb"],"favorites":{"Adam Rich":1,"Brad Rubinstein":2,"Jason Hall":0,"Jonathan Gordon":0,"Paul Willmott":1}}

The jsond language supports all of the JSON specification in JSON values, as well as regular racket comments between value definitions:

#lang jsond

#:name abc "abc"

;; comment

#:name num 123

#:name array [1, 2, {"xyz": "abc"}, true, false, null]

Examples:

> (require jsond/examples/data)
> abc
"abc"
> num
123
> array
'(1 2 #hasheq((xyz . "abc")) #t #f null)

2 Syntax🔗ℹ

	‹jsond›	::=	‹name-json›*
	‹name-json›	::=	#:name ‹id› ‹json›

There may be any style of racket comment between ‹name-json›s. Each use of #:name, ‹id›, and ‹json› must be whitespace-separated. ‹json› can be any valid JSON value as determined by read-json. ‹id› can be any valid Racket identifier.

3 Semantics🔗ℹ

The jsond language produces a module that provides each of the ‹id›s as a binding to the jsexpr? corresponding to the adjacent ‹json›.

The module has a submodule main that, when run, calls write-json on a hash mapping each provided ‹id› to its value.