When occurring other than as the first argument of a disjunction operator
;/2), this is equivalent to:
P -> Q ; fail.
This is not normally regarded as a built-in
predicate, since it is part of the syntax of the language. However,
it is like a built-in predicate in that you can say
‘->’ cuts away any choice points in the execution of P
Note that the operator precedence of ‘->’ is greater than 1000, so it dominates commas. Thus, in:
f :- p, q -> r, s. f.
‘->’ cuts away any choices in
p or in
q, but unlike
!) it does not cut away the alternative choice for
Cuts in P do not make sense, but they are allowed, their scope being the goal P. The scope of cuts in Q extends to the containing clause.
Depends on Q.
Call errors (see ref-sem-exc).