JSON Module¶

The py.json standard library module provides relational predicates for parsing, generating, and querying JSON data. JSON objects map to DictTerm for unification-aware access.

The implementation lives in clausal/modules/py/json.py.

Import¶

-import_from(py.json, [Parse, Generate, PrettyGenerate, Get, ReadFile, WriteFile])

Or via module import:

-import_module(py.json)
# then use py.json.Parse(S_, T_), py.json.Get(T_, "key", V_), etc.

Type Mapping¶

JSON	Clausal
`{}` object	`DictTerm`
`[]` array	Python `list`
`"string"`	Python `str`
`123` / `1.5`	Python `int` / `float`
`true`/`false`	Python `True`/`False`
`null`	Python `None`

Conversion is recursive: nested JSON objects produce nested DictTerms.

Predicates¶

Parse/2¶

Parse(String, Term) — parse a JSON string into Clausal terms. Fails on invalid JSON or unbound String.

parse_config(S, CONFIG) <- Parse(S, CONFIG)

Generate/2¶

Generate(Term, String) — serialize a Clausal term to a compact JSON string. Fails if the term contains unbound variables.

to_json(DATA, JSON) <- Generate(DATA, JSON)

PrettyGenerate/2¶

PrettyGenerate(Term, String) — like Generate but with 2-space indentation.

Get/3¶

Get(Term, Key, Value) — extract a value from a DictTerm by key.

Key bound: direct lookup, unify Value. Fails if key not found.
Key unbound: enumerate all key-value pairs via backtracking.

-import_from(py.json, [Parse, Get])

get_name(JSON_STRING, NAME) <- (
    Parse(JSON_STRING, DATA),
    Get(DATA, "name", NAME)
)

ReadFile/2¶

ReadFile(Path, Term) — read and parse a JSON file. Fails on file or parse error.

load_config(CONFIG) <- ReadFile("config.json", CONFIG)

WriteFile/2¶

WriteFile(Path, Term) — serialize a term and write to a JSON file (2-space indented). Fails if term contains unbound variables.

Example¶

-import_from(py.json, [Parse, Generate, Get, ReadFile])

load_config(CONFIG) <- ReadFile("config.json", CONFIG)

get_setting(CONFIG, KEY, VALUE) <- Get(CONFIG, KEY, VALUE)

config_to_json(CONFIG, JSON) <- Generate(CONFIG, JSON)