= json: readjson, writejson, JValue: read, write and represent values in JavaScript Object Notation     include "json.m";    json := load JSON JSON->PATH;     JValue: adt {        pick{        Object =>            mem:   cyclic list of (string, ref JValue);        Array =>            a:     cyclic array of ref JValue;        String =>            s:     string;        Int =>            value: big;        Real =>            value: real;        True or        False or        Null =>        }        isarray:   fn(v: self ref JValue): int;        isfalse:   fn(v: self ref JValue): int;        isint:     fn(v: self ref JValue): int;        isnull:    fn(v: self ref JValue): int;        isnumber:  fn(v: self ref JValue): int;        isobject:  fn(v: self ref JValue): int;        isreal:    fn(v: self ref JValue): int;        isstring:  fn(v: self ref JValue): int;        istrue:    fn(v: self ref JValue): int;        copy:      fn(v: self ref JValue): ref Jvalue;        eq:        fn(v: self ref JValue, v: ref JValue): int;        get:       fn(v: self ref JValue, mem: string): ref JValue;        set:       fn(v: self ref JValue, mem: string, value: ref JValue);        text:      fn(v: self ref JValue): string;    };        init:      fn(bufio: Bufio);    readjson:  fn(input: ref Bufio->Iobuf): (ref JValue, string);    writejson: fn(output: ref Bufio->Iobuf, val: ref JValue): int;        jvarray:   fn(a: array of ref JValue): ref JValue.Array;    jvbig:     fn(b: big): ref JValue.Int;    jvfalse:   fn(): ref JValue.False;    jvint:     fn(i: int): ref JValue.Int;    jvnull:    fn(): ref JValue.Null;    jvobject:  fn(m: list of (string, ref JValue)): ref JValue.Object;    jvreal:    fn(r: real): ref JValue.Real;    jvstring:  fn(s: string): ref JValue.String;    jvtrue:    fn(): ref JValue.True;    JSON provides value representations, and encoding and  decod‐ing  operations  for  the  JavaScript  Object Notation (JSON)described by Internet RFC4627 and summarised in json(6). Init must be called before invoking any  other  operation  ofthe  module.   The bufio parameter must refer to the instanceof bufio(2) that provides the Iobuf parameters used for inputand output. JValue  is  the internal representation of values transmittedby the JSON encoding.  They are distinguished in a pick adt: JValue.False       Represents the value false. JValue.Null       Represents a null value of any type. JValue.True       Represents the value true. JValue.Int       Represents as a Limbo big a JavaScript number with  no       fractional part. JValue.Real       Represents  as a Limbo real a JavaScript number with a       fractional part. JValue.String       Represents a JavaScript string of  Unicode  characters       from +U'0000' to +U'FFFF'. JValue.Array       Represents a JavaScript array of values of any type. JValue.Object       Represents  a  tuple  of (member/property name, value)       pairs corresponding  to  the  value  of  a  JavaScript       object,  or  an associative array or table, indexed by       strings.  The member names must  be  unique  within  a       value. Readjson  reads  a single value in JSON format from the inputstream and returns a tuple (val, err).  On success, val is  aJValue  that  represents  the value successfully read.  If anerror occurs, val is nil and err contains a diagnostic. Writejson writes to the output stream in JSON format a repre‐sentation  of the value v.  It returns 0 on success and -1 onerror (setting the system error string). The easiest way to create a new JValue for subsequent  outputis  with  one  of  the module-level functions jvarray, jvint,jvobject, jvstring, and so on.  As values of a  pick  adt,  aJValue  can be inspected using Limbo's tagof operator and theappropriate variant accessed using a pick statement.   JValuealso  supports  several  groups  of  common  operations,  forsmaller, tidier code.  First, the set  of  enquiry  functionsv.isX()  return  true  if  the  value v is an instance of theJavaScript type X (array, int, object, real, string, etc).  Anumeric  value  is  either int or real.  The other operationsare: v.copy()       Return a (reference to) a copy of value v.  The  copy‐       ing is not recursive. v.eq(w)       Return  true  if  the  values  of  v  and w are equal,       including the values of  corresponding  subcomponents,       recursively v.get(mem)       Return  the value associated with the member named mem       in v; return null if there is none. v.set(mem, value)       Adds or changes the value associated with  the  member       named  mem in v, which must be a JValue.Object( raises       exception json: set non-object otherwise). v.text()       Return a string containing the JSON representation  of       v. == source/appl/lib/json.b == see ALSOsexprs(2), ubfa(2), json(6), sexprs(6), ubfa(6)D Crockford, ``The application/json Media Type for JavaScriptObject Notation (JSON)'', RFC4627.