41 lines
1.1 KiB
Kotlin
41 lines
1.1 KiB
Kotlin
package prolog.logic
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import prolog.ast.terms.CompoundTerm
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import prolog.ast.terms.Term
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import prolog.ast.terms.Variable
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/**
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* True if [Term] is bound (i.e., not a variable) and is not compound.
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* Thus, atomic acts as if defined by:
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*
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* atomic(Term) :-
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* nonvar(Term),
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* \+ compound(Term).
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*/
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fun atomic(term: Term): Boolean = nonvariable(term) && !compound(term)
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/**
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* True if [Term] is bound to a compound term.
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* See also functor/3 =../2, compound_name_arity/3 and compound_name_arguments/3.
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*/
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fun compound(term: Term): Boolean {
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val isCompound = term is CompoundTerm
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val isVariableCompound = term is Variable && term.alias().isPresent && compound(term.alias().get())
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return isCompound || isVariableCompound
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}
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/**
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* True if [Term] currently is not a free variable.
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*/
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fun nonvariable(term: Term): Boolean = !variable(term)
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/**
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* True if [Term] currently is a free variable.
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*/
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fun variable(term: Term): Boolean {
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if (term is Variable) {
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return term.alias().isEmpty || term.alias().get() === term || variable(term.alias().get())
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}
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return false
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}
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