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/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Safe type tests
===============
"si" stands for "sufficiently instantiated".
These predicates:
- throw instantiation errors if the argument is
not sufficiently instantiated to make a sound decision
- succeed if the argument is of the specified type
- fail otherwise.
For instance, atom_si(A) yields an *instantiation error* if A is a
variable. This is logically sound, since in that case the argument
is not sufficiently instantiated to make any decision.
The definitions are taken from:
https://stackoverflow.com/questions/27306453/safer-type-tests-in-prolog
"si" can also be read as "safe inference", so possibly also other
predicates are candidates for this library.
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
:- module(si, [atom_si/1,
integer_si/1,
atomic_si/1,
list_si/1]).
:- use_module(library(lists)).
atom_si(A) :-
functor(A, _, 0), % for the instantiation error
atom(A).
integer_si(I) :-
functor(I, _, 0),
integer(I).
atomic_si(AC) :-
functor(AC,_,0).
list_si(L) :-
\+ \+ length(L, _),
sort(L, _).
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