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pl:prolog:pllib:meta_interpreter_tracing [2019/06/27 15:50] |
pl:prolog:pllib:meta_interpreter_tracing [2019/06/27 15:50] (aktualna) |
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| + | ====== Meta interpreter tracing ====== | ||
| + | {{tag>metainterpreter}} | ||
| + | ===== Description ===== | ||
| + | A Prolog meta-interpreter for tracing programs | ||
| + | |||
| + | **Source**: PROLOG programming for artificial intelligence, 3rd Edition, Harlow, 2001, ISBN 0-201-40375-7. | ||
| + | ===== Download ===== | ||
| + | Program source code: {{meta_interpreter_tracing.pl}} | ||
| + | ===== Listing ===== | ||
| + | <code prolog> | ||
| + | % Figure 23.2 A Prolog meta-interpreter for tracing programs | ||
| + | % in pure Prolog. | ||
| + | |||
| + | |||
| + | % trace( Goal): execute Prolog goal Goal displaying trace information | ||
| + | |||
| + | trace( Goal) :- | ||
| + | trace( Goal, 0). | ||
| + | |||
| + | trace( true, Depth) :- !. % Red cut; Dept = depth of call | ||
| + | |||
| + | trace( ( Goal1, Goal2), Depth) :- !, % Red cut | ||
| + | trace( Goal1, Depth), | ||
| + | trace( Goal2, Depth). | ||
| + | |||
| + | trace( Goal, Depth) :- | ||
| + | display( 'Call: ', Goal, Depth), | ||
| + | clause( Goal, Body), | ||
| + | Depth1 is Depth + 1, | ||
| + | trace( Body, Depth1), | ||
| + | display( 'Exit: ', Goal, Depth), | ||
| + | display_redo( Goal, Depth). | ||
| + | |||
| + | trace( Goal, Depth) :- % All alternatives exhausted | ||
| + | display( 'Fail: ', Goal, Depth), | ||
| + | fail. | ||
| + | |||
| + | display( Message, Goal, Depth) :- | ||
| + | tab( Depth), write( Message), | ||
| + | write( Goal), nl. | ||
| + | |||
| + | display_redo( Goal, Depth) :- | ||
| + | true % First succeed simply | ||
| + | ; | ||
| + | display( 'Redo: ', Goal, Depth), % Then announce backtracking | ||
| + | fail. % Force backtracking | ||
| + | </code> | ||
| + | ===== Comments ===== | ||
