debugfinds(expression,sentence,factset,ruleset) → expressionlist
The debugfinds subroutine takes as arguments an expression (called the aspect), a sentence (called the query), a dataset, and a ruleset. It uses the facts in the dataset and the rules in the ruleset (and the definitions of predefined functions and relations) to derive all instance of the query. It returns a list of all instances of the aspect for each query instance it finds; if it fails to derive any instances of the query, it returns [].
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Call: definefacts(repository,readdata('p(art,bob) p(bob,cal) p(bob,cam)'))
Exit: true
Call: definerules(library,readdata('g(X,Z) :- p(X,Y) & p(Y,Z)'))
Exit: true
Call: debugfinds('Z',read('g(art,Z)'),repository,library)
Exit: [cal,cam]
Call: debugfinds('X',read('g(art,cal)'),repository,library)
Exit: [art]
Call: debugfinds(read('answer(X,Z)'),read('g(X,Z)'),repository,library)
Exit: [answer(art,cal), answer(art,cam)]
Call: debugfinds(read('answer(X,Z)'),read('p(X,Y) & p(Y,Z)'),repository,library)
Exit: [answer(art,cal), answer(art,cam)]
Call: debugfinds('Z',read('g(bob,Z)'),repository,library)
Exit: []
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The subroutine debugfinds differs from compfinds in two ways. (1) It limits the depth of recursion based on the value of the global variable depth. (2) It allows the user to trace attempts to compute relations specified via the value of the variable traces (which can be modified directly or using the trace and untrace subroutines). Trace output is printed using the Javascript subroutine console.log.
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