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phrase(+Grammar, ?Tokens, ?Remainder)

Succeeds if Tokens can be parsed as part of the grammar defined in Grammar and Remainder contains any remaining terms in Tokens.

Grammar: Compound Term or Atom.
Tokens: List of Prolog terms.
Remainder: List of Prolog terms.

Description

phrase/3 is used to parse grammars (DCGs) defined using the grammar rule operator -->. The flag macro_expansion must be set on when compiling grammar rules.

Giving a list of terms in Tokens, phrase/3 parses it according to the grammar defined in Grammar. As the terms in Tokens are parsed in order, any remaining terms are returned in Remainder. Further acceptable solutions are returned on backtracking.

Modes and Determinism

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

Modules

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

Fail Conditions

The initial terms in Tokens do not belong to Grammar

Resatisfiable

Depends on the grammar

Exceptions

(4) instantiation fault: Grammar is not instantiated.
(5) type error: Grammar is a number or a string.

Examples

   [eclipse]: [user].
    a --> [].
    a --> [z],a.
    user compiled 212 bytes in 0.03 seconds
   yes.
   [eclipse]: phrase(a,[z,z],[]).

   yes.
   [eclipse]: phrase(a,[z,z,z,y],[z,y]).

   yes.
   [eclipse]: phrase(a,[z,z,y],R).

   R = [z, z, y]     More? (;)

   R = [z, y]     More? (;)

   R = [y]     More? (;)

   no (more) solution.
   [eclipse]: phrase(a,X,[y]).

   X = [y]     More? (;)

   X = [z, y]     More? (;)

   X = [z, z, y]     More? (;)

   X = [z, z, z, y]     More? (;)

   X = [z, z, z, z, y]     More? (;)
   yes.
   [eclipse]:

Fail:
   phrase(a, [z, z, y], []).

Error:
   phrase(X, [what, time, is, it], [is, it],R).  (Error 4).
   phrase("a", X,R).                             (Error 5).
   phrase(456, X,R).                             (Error 5).