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json_prolog/2

Module​

This predicate is provided by json.pl.

Load this module before using the predicate:

:- consult('/v1/lib/json.pl').

Description​

Relates JSON text with its canonical Prolog representation.

Json is text: an atom, a list of characters, or a list of character codes.

The canonical representation for Term is:

  • JSON objects are represented as json(NameValueList);
  • JSON arrays are represented as Prolog lists;
  • JSON strings are represented as atoms;
  • JSON numbers are represented as numbers;
  • JSON booleans and null are represented as @(true), @(false), and @(null).

Signature​

json_prolog(?Json, ?Term) is det

Examples​

Decode JSON text into a canonical Prolog term​

This scenario demonstrates how JSON objects, strings, and booleans are represented in Prolog.

Here are the steps of the scenario:

  • Given the query:
consult('/v1/lib/json.pl'),
json_prolog('{"foo":"bar","ok":true}', Term).
  • When the query is run
  • Then the answer we get is:
height: 42
gas_used: 12069
answer:
  has_more: false
  variables: ["Term"]
  results:
  - substitutions:
    - variable: Term
      expression: "json([foo=bar,ok= @(true)])"

Encode a canonical Prolog term as JSON text​

This scenario demonstrates how a canonical Prolog JSON object is encoded as compact JSON text.

Here are the steps of the scenario:

  • Given the query:
consult('/v1/lib/json.pl'),
json_prolog(Json, json([foo=bar,ok= @(true)])).
  • When the query is run
  • Then the answer we get is:
height: 42
gas_used: 11049
answer:
  has_more: false
  variables: ["Json"]
  results:
  - substitutions:
    - variable: Json
      expression: "'{\"foo\":\"bar\",\"ok\":true}'"
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