JSON recipes

Practical examples for reading, writing, and converting JSON using PyLog’s built‑ins. Use these snippets in the REPL or embed PyLog in Python.

Parse JSON text (classic)

?- atom_json_term('{"name":"test","value":42}', T, []).
T = json([name=test, value=42]).

Parse JSON text (dict)

?- atom_json_term('{"name":"alice","age":30}', D, [mode(dict)]).
D = {name:alice, age:30}.

?- atom_json_term('{"name":"alice","age":30}', D, [json_object(dict)]).
D = {name:alice, age:30}.

Serialize term to JSON

?- T = json([inner=json([value=42])]), atom_json_term(A, T, []).
A = '{"inner": {"value": 42}}'.

Round‑trip (dict)

?- atom_json_term('{"ok":true}', D, [mode(dict)]), atom_json_term(A, D, [mode(dict)]).
D = {ok:true},
A = '{"ok": true}'.

Constants (classic)

?- atom_json_term('{"xs":[null,true,false]}', T, []).
T = json([xs=[@(null), @(true), @(false)]]).

Dict updates

?- dict_create(D0, none, [count-1]), put_dict([count-2, added-yes], D0, D1), get_dict(count, D1, V).
D0 = {count:1},
D1 = {added:yes, count:2},
V = 2.

Notes

• Prefer atom_json_term/3 in pure Prolog. json_read/3 and json_write/3 work with file‑like streams when embedding PyLog in Python.
• JSON objects are unordered; PyLog uses canonical key sorting.
• Special floats (NaN, ±Inf) are rejected.
• Dict mode uses atoms true/false/null; strings "true"/"false" map to the same atoms.