A.46 library(terms): Term manipulation

Compatibility

YAP, SICStus, Quintus. Not all versions of this library define exactly the same set of predicates, but defined predicates are compatible.

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

[det]term_size(@Term, -Size)

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.

[semidet]variant(@Term1, @Term2)

Same as SWI-Prolog Term1 =@= Term2.

subsumes_chk(@Generic, @Specific)

True if Generic can be made equivalent to Specific without changing Specific.

deprecated

Replace by subsumes_term/2.

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.

[det]term_subsumer(+Special1, +Special2, -General)

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

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)].

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.

[semidet]same_functor(?Term1, ?Term2)

[semidet]same_functor(?Term1, ?Term2, -Arity)

[semidet]same_functor(?Term1, ?Term2, ?Name, ?Arity)

True when Term1 and Term2 are compound 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.

Compatibility

SICStus