JSON¶

(kaappi json) — JSON parser and serializer. Pure Scheme, no build step.

thottam install kaappi-json

Quick start¶

(import (kaappi json))

;; Parse JSON
(json-read-string "{\"name\": \"Alice\", \"age\": 30}")
;; => (("name" . "Alice") ("age" . 30))

;; Serialize to JSON
(json-write-string '(("name" . "Alice") ("age" . 30)))
;; => "{\"name\":\"Alice\",\"age\":30}"

Type mapping¶

JSON	Scheme	Example
object	alist	`(("key" . "value"))`
array	list	`(1 2 3)`
string	string	`"hello"`
number (integer)	exact integer	`42`
number (float)	inexact number	`3.14`
`true`	`#t`
`false`	`#f`
`null`	`'null` symbol

Vectors are written as JSON arrays: #(1 2 3) becomes [1,2,3].

API¶

Reading¶

(json-read [port])          ; parse JSON from port (default: current-input-port)
(json-read-string str)      ; parse JSON from a string

Writing¶

(json-write val [port])     ; write JSON to port (default: current-output-port)
(json-write-string val)     ; write JSON to a string

Null¶

(json-null)                 ; the null value ('null symbol)
(json-null? val)            ; test for null

Examples¶

Nested objects¶

(json-read-string "{\"user\": {\"id\": 1, \"tags\": [\"admin\", \"active\"]}}")
;; => (("user" . (("id" . 1) ("tags" . ("admin" "active")))))

Building JSON from data¶

(json-write-string
  `(("users" . ,(map (lambda (name)
                       `(("name" . ,name)))
                     '("Alice" "Bob" "Charlie")))))
;; => "{\"users\":[{\"name\":\"Alice\"},{\"name\":\"Bob\"},{\"name\":\"Charlie\"}]}"

Reading from a file¶

(let ((port (open-input-file "config.json")))
  (let ((config (json-read port)))
    (close-input-port port)
    config))

Features¶

Full JSON spec compliance (RFC 8259)
Unicode escape sequences (\uXXXX) including surrogate pairs
All escape sequences (\", \\, \/, \b, \f, \n, \r, \t)
Scientific notation (1.5e-3)
Round-trip safe (parse then serialize preserves structure)