Add FFI for json (#11)

Adds FFI definitions for core/json along with a JSON parser and printer. Printer doesn't support pretty printing yet.

json/spago.yaml

@@ -0,0 +1,18 @@
+package:
+  name: json
+  dependencies:
+  - prelude
+  - arrays
+  - functions
+  - integers
+  - maybe
+  - either
+  - tuples
+  - foldable-traversable
+  - gen
+  - strings
+  - unfoldable
+  test:
+    main: Test.JSON.Main
+    dependencies:
+      - assert

json/src/JSON.purs

@@ -30,7 +30,7 @@ import Data.Function.Uncurried (runFn2, runFn3, runFn7)
 import Data.Int as Int
 import Data.Maybe (Maybe(..))
 import JSON.Internal (JArray, JObject, JSON)
-import JSON.Internal (JArray, JObject, JSON) as Exports
+import JSON.Internal (JArray, JObject, JSON, isNull) as Exports
 import JSON.Internal as Internal
 
 -- | Attempts to parse a string as a JSON value. If parsing fails, an error message detailing the

json/src/JSON.ss

@@ -0,0 +1,31 @@
+(library (JSON foreign)
+  (export _null
+          fromBoolean
+          fromInt
+          fromString
+          fromJArray
+          fromJObject
+          print
+          printIndented)
+  (import (chezscheme)
+          (only (JSON.Internal foreign) json-stringify))
+
+  (define (coerce x) x)
+
+  (define _null 'null)
+
+  (define fromBoolean coerce)
+
+  (define fromInt inexact)
+
+  (define fromString coerce)
+
+  (define fromJArray coerce)
+
+  (define fromJObject coerce)
+
+  (define print json-stringify)
+
+  (define printIndented json-stringify)
+
+  )

json/src/JSON/Array.ss

@@ -0,0 +1,9 @@
+(library (JSON.Array foreign)
+  (export singleton)
+  (import (chezscheme)
+          (prefix (purs runtime srfi :214) srfi:214:))
+
+  (define (singleton x) (srfi:214:flexvector x))
+
+  )
+

json/src/JSON/Internal.js

@@ -57,3 +57,5 @@ export const _index = (nothing, just, ix, arr) =>
   ix >= 0 && ix < arr.length ? just(arr[ix]) : nothing;
 
 export const _append = (xs, ys) => xs.concat(ys);
+
+export const isNull = (json) => json == null;

json/src/JSON/Internal.purs

@@ -140,3 +140,5 @@ foreign import _append
        JArray
        JArray
        JArray
+
+foreign import isNull :: JSON -> Boolean