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ILOG OPL Development Studio Language Reference Manual

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A logical constraint between interval variables: presenceOfThe presence constraint states a certain interval must be present in the solution.The semantics of the presence constraint on a fixed interval is simply: presenceOf( ) x( ).The truth value of this constraint can be used in arithmetical expressions, and thereby restrictedby logical constraints.This constraint can be used in meta-constraints to indicate, for example, that there may betwo optional intervals a and b; if interval a is present then b must be present as well. This ismodelled by the constraint presenceOf(a) presenceOf(b).<strong>OPL</strong> formulationThe constraint to express that the interval variable must be present:presenceOf(a);where:dvar interval a;For an example of the presenceOf constraint see presenceOf in the <strong>OPL</strong> <strong>Language</strong> Quick<strong>Reference</strong>.I L O G O P L D E V E L O P M E N T S T U D I O L A N G U A G ER E F E R E N C E M A N U A L155

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