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apply_macros.pl -- Goal expansion rules to avoid meta-calling
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This module defines goal_expansion/2 rules to deal with commonly used, but fundamentally slow meta-predicates. Notable maplist/2... defines a useful set of predicates, but its execution is considerable slower than a traditional Prolog loop. Using this library calls to maplist/2... are translated into an call to a generated auxiliary predicate that is compiled using compile_aux_clauses/1. Currently this module supports:

The idea for this library originates from ECLiPSe and came to SWI-Prolog through YAP.

- Jan Wielemaker
To be done
- Support more predicates
Source expand_maplist(+Callable, +Lists, -Goal) is det[private]
Macro expansion for maplist/2 and higher arity.
Source expand_apply(+GoalIn:callable, -GoalOut) is semidet[private]
Macro expansion for `apply' predicates.
Source expand_apply(+GoalIn:callable, -GoalOut, +PosIn, -PosOut) is semidet[private]
Translation of simple meta calls to inline code while maintaining position information. Note that once(Goal) cannot be translated to (Goal->true) because this will break the compilation of (once(X) ; Y). A correct translation is to (Goal->true;fail). Abramo Bagnara suggested ((Goal->true),true), which is both faster and avoids warning if style_check(+var_branches) is used.
Source expand_phrase(+PhraseGoal, -Goal) is semidet
Source expand_phrase(+PhraseGoal, +Pos0, -Goal, -Pos) is semidet
Provide goal-expansion for PhraseGoal. PhraseGoal is either phrase/2,3 or call_dcg/2,3. The current version does not translate control structures, but only simple terminals and non-terminals.

For example:

?- expand_phrase(phrase(("ab", rule)), List), Goal).
Goal = (List=[97, 98|_G121], rule(_G121, [])).
- Re-throws errors from dcg_translate_rule/2
Source dcg_extend(+Callable, +Pos0, -Goal, -Pos, +Xs0, ?Xs) is semidet[private]
Source qcall_instantiated(@Term) is semidet[private]
True if Term is instantiated sufficiently to call it.
To be done
- Shouldn't this be callable straight away?