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terms.pl -- Term manipulation
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Compatibility library for term manipulation predicates. Most predicates in this library are provided as SWI-Prolog built-ins.

Compatibility
- YAP, SICStus, Quintus. Not all versions of this library define exactly the same set of predicates, but defined predicates are compatible.
Source term_size(@Term, -Size) is det
True if Size is the size in cells occupied by Term on the global (term) stack. A cell is 4 bytes on 32-bit machines and 8 bytes on 64-bit machines. The calculation does take sharing into account. For example:
?- A = a(1,2,3), term_size(A,S).
S = 4.
?- A = a(1,2,3), term_size(a(A,A),S).
S = 7.
?- term_size(a(a(1,2,3), a(1,2,3)), S).
S = 11.

Note that small objects such as atoms and small integers have a size 0. Space is allocated for floats, large integers, strings and compound terms.

Source variant(@Term1, @Term2) is semidet
Same as SWI-Prolog Term1 =@= Term2.
Source subsumes_chk(@Generic, @Specific)
True if Generic can be made equivalent to Specific without changing Specific.
deprecated
- Replace by subsumes_term/2.
Source subsumes(+Generic, @Specific)
True if Generic is unified to Specific without changing Specific.
deprecated
- It turns out that calls to this predicate almost always should have used subsumes_term/2. Also the name is misleading. In case this is really needed, one is adviced to follow subsumes_term/2 with an explicit unification.
Source term_subsumer(+Special1, +Special2, -General) is det
General is the most specific term that is a generalisation of Special1 and Special2. The implementation can handle cyclic terms.
author
- Inspired by LOGIC.PRO by Stephen Muggleton
Compatibility
- SICStus
Source term_factorized(+Term, -Skeleton, -Substiution)
Is true when Skeleton is Term where all subterms that appear multiple times are replaced by a variable and Substitution is a list of Var=Value that provides the subterm at the location Var. I.e., After unifying all substitutions in Substiutions, Term == Skeleton. Term may be cyclic. For example:
?- X = a(X), term_factorized(b(X,X), Y, S).
Y = b(_G255, _G255),
S = [_G255=a(_G255)].
Source mapargs(:Goal, ?Term1, ?Term2)
Term1 and Term2 have the same functor (name/arity) and for each matching pair of arguments call(Goal, A1, A2) is true.
Source mapsubterms(:Goal, +Term1, -Term2) is det
Recursively map sub terms of Term1 into subterms of Term2 for every pair for which call(Goal, ST1, ST2) succeeds. Procedurably, the mapping for each (sub) term pair T1/T2 is defined as:
  • If T1 is a variable, Unify T2 with T1.
  • If call(Goal, T1, T2) succeeds we are done. Note that the mapping does not continue in T2. If this is desired, Goal must call mapsubterms/3 explicitly as part of it conversion.
  • If T1 is a dict, map all values, i.e., the tag and keys are left untouched.
  • If T1 is a list, map all elements, i.e., the list structure is left untouched.
  • If T1 is a compound, use same_functor/3 to instantiate T2 and recurse over the term arguments left to right.
  • Otherwise T2 is unified with T1.
Source same_functor(?Term1, ?Term2) is semidet
Source same_functor(?Term1, ?Term2, -Arity) is semidet
Source same_functor(?Term1, ?Term2, ?Name, ?Arity) is semidet
True when Term1 and Term2 are terms that have the same functor (Name/Arity). The arguments must be sufficiently instantiated, which means either Term1 or Term2 must be bound or both Name and Arity must be bound.

If Arity is 0, Term1 and Term2 are unified with Name for compatibility.

Compatibility
- SICStus

Undocumented predicates

The following predicates are exported, but not or incorrectly documented.

 term_hash(Arg1, Arg2)
 cyclic_term(Arg1)
 term_hash(Arg1, Arg2, Arg3, Arg4)
 term_variables(Arg1, Arg2, Arg3)
Source same_functor(Arg1, Arg2, Arg3, Arg4)
Source same_functor(Arg1, Arg2, Arg3)