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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 =====
  
pl/prolog/pllib/meta_interpreter_tracing.txt · ostatnio zmienione: 2019/06/27 15:50 (edycja zewnętrzna)
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