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phrase(+Grammar, ?List)

Succeeds if List unifies with a list from the specified grammar Grammar.

Grammar: Compound term or Atom.
List: List of grammar terminals (prolog terms).

Description

phrase/2 can be use as a recognizer or as a generator of grammars. As a recognizer, it succeeds or fails if term belongs or not to the specified grammar Grammar. As a generator, it generates on backtracking all the elements of the grammar.

A grammar is specified by setting the flag macro_expansion to on and by compiling clauses using the DCG operator -->.

Modes and Determinism

phrase(+, ++) is semidet
phrase(+, -) is nondet

Modules

This predicate is sensitive to its module context (tool predicate, see @/2).

Fail Conditions

List does not belong to Grammar

Resatisfiable

Depends on the particular grammar

Exceptions

(4) instantiation fault: Grammar is not instantiated.
(5) type error: Grammar is a number or a string (i.e. not a valid DCG head).

Examples

   [eclipse]: sh('cat gram.pl').
   sentence --> noun_phrase, verb_phrase.
   noun_phrase --> article, noun.
   verb_phrase --> verb | verb, noun_phrase.
   article --> [the].
   noun --> [compiler].
   noun --> [program].
   verb --> [compiles].
   yes.
   [eclipse]: [gram].
   /home/user/gram.pl        compiled 732 bytes in 0.37 seconds
   yes.
   [eclipse]: phrase(sentence,[the,compiler,compiles]).
   yes.
   [eclipse]: phrase(sentence,[the,compiler,compiles,the,program]).
   yes.
   [eclipse]: phrase(sentence, X).

   X = [the, compiler, compiles]     More? (;)

   X = [the, compiler, compiles, the, compiler]     More? (;)

   X = [the, compiler, compiles, the, program]     More? (;)

   X = [the, program, compiles]     More? (;)

   X = [the, program, compiles, the, compiler]     More? (;)

   X = [the, program, compiles, the, program]
   yes.
   [eclipse]:

Fail:
   phrase(sentence, [not, a, sentence]).

Error:
   phrase(X, [what, time, is, it]).    (Error 4).
   phrase("sentence", X).              (Error 5).
   phrase(123, X).                     (Error 5).