first

Syntax

constraint first(sequenceVar seq, intervalVar interval)

Parameters

• seq: sequence variable.
• interval: interval variable.

Description

This function returns a constraint that states that whenever interval variable interval is present, it must be ordered first in the sequence variable seq.

Example

a = intervalVar(size=5);
b = intervalVar(size=6);
c = intervalVar(optional, size=7);
// A sequence variable defined on {a, b, c}
seq = sequenceVar([a, b, c]);
// The interval variables of the sequence cannot overlap
noOverlap(seq);
// If interval variable c is present, it must be the first one in the sequence
first(seq, c);

Requirements

• interval should be an interval variable of sequence variable seq.