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< title > Logtalk control construct: :/1< / title >
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< div class = "top-left" > Logtalk reference manual< / div >
< div class = "top-right" > Control construct: :/1< / div >
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< div class = "navtop" > < a href = "../../index.html" > contents< / a > > < a href = "../index.html" > reference manual< / a > > < a href = "../index.html#constructs" > control constructs< / a > < / div >
< h2 id = "control_direct1" class = "codenp" > :/1< / h2 >
< h4 > Description< / h4 >
< pre > :Goal< / pre >
< p >
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Calls an imported category predicate without using the message sending mechanisms. The category predicate is called with the same execution context (< em > sender< / em > , < em > this< / em > , and < em > self< / em > ) as the predicate whose body contains the call. The lookup for both the predicate declaration and the predicate definition begins in < em > this< / em > instead of < em > self< / em > . Furthermore, the lookup of the predicate definition is restricted to the imported categories. As a consequence, any redeclaration or redefinition of the predicate in a descendant of the object containing the call will be ignored.
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< / p >
< h4 > Template and modes< / h4 >
< pre > :+callable< / pre >
< h4 > Errors< / h4 >
< dl >
< dt > Goal is a variable:< / dt >
< dd > < code > instantiation_error< / code > < / dd >
< dt > Goal is neither a variable nor a callable term:< / dt >
< dd > < code > type_error(callable, Goal)< / code > < / dd >
< dt > The object containing the call does not import any category:< / dt >
< dd > < code > existence_error(procedure, Goal)< / code > < / dd >
< / dl >
< h4 > Examples< / h4 >
< pre > :- object(bounded_point,
imports(bounded_coordinate),
instantiates(class),
specializes(point)).
move(X, Y) :-
:check_bounds(x, X), % defined in the "bounded_coordinate" category
:check_bounds(y, Y),
^^move(X, Y).< / pre >
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< span > Copyright © < a href = "mailto:pmoura@logtalk.org" > Paulo Moura< / a > — < a href = "http://logtalk.org" > Logtalk.org< / a > < / span > < br / >
2007-11-06 01:50:09 +00:00
< span > Last updated on: August 27, 2007< / span >
2007-06-12 11:39:47 +01:00
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