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prune_instances(+List, -PrunedList)
Succeeds if PrunedList is the smallest list that subsumes the list List.
- List
- List of instantiated terms.
- PrunedList
- List or variable.
Description
Used to get the smallest list PrunedList whose elements subsume elements
of the list List. List must not contain variables. If List contains
elements which are variants of each other, then of these, PrunedList
will only contain the first element found. If List contains element(s)
which are instances of another element, then of these, PrunedList will
only contain the latter.
Note that if List contains only ground terms, it cannot contain proper
instances or variants, but only duplicates. Therefore, it is faster to
use a sorting predicate to prune it.
Modes and Determinism
- prune_instances(+, -) is det
Examples
Success:
prune_instances([5,2,3,5,4,2],L).
(gives L=[5,2,3,4]).
prune_instances([f(1,2),f(1,M),1],L). % instance
(gives L=[f(1,M),1]).
prune_instances([f(1,2,3),f(1,M,3),f(1,2,N)],L).
(gives L=[f(1,M,3),f(1,2,N)]).
prune_instances([f(1,N),f(1,M),1],L). % variants (first one retained)
(gives L=[f(1,N),1]).
prune_instances([f(1,X),f(1,2),g(1)],L).
(gives L=[f(1,X),g(1)]).
:- lib(ic).
X::2..5, prune_instances([1,3,X,5,8], L).
(gives L=[X,1,8]).
Fail:
prune_instances([1,2,3,1,4,2],[2,3,4]).
See Also
sort / 2, sort / 4