Section "expansion"

We only provide shallow term expansion. Shallow term expansion can be defined via the multi-file predicate term_expansion/2, but there is no automatic call of goal_expansion/2 for any subgoals in the directive or clause provided as a term. The Prolog system comes with term expansion for definite clause grammars (DCG).

The following expansion predicates are provided:

term_expansion(C, D):

This predicate can be used to define custom term expansion rules.

expand_term(C, D):

The predicate succeeds in D with the expansion of the term C.

P --> Q: [DCG 7.13.2]

P, R --> Q: [DCG 7.13.2]

The fact is transformed into the DCG clause for the DCG non-terminal P and the DCG body Q. The ternary form allows an additional DCG push back R.

phrase(B, I, O): [DCG 8.1.1]

The predicate succeeds whenever the DCG body B succeeds for the input I and the output O.

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