before

OPL function (scheduling) to sequence interval variables

Purpose

OPL function (scheduling) to sequence interval variables.

type
boolean

Syntax

before(p, a, b)

Where:

dvar interval a;
dvar interval b;
dvar sequence p;

Description

States that if intervals a and b are present, a will appear before b in the sequence p; other intervals may be ordered in between the two. Compare before with prev (scheduling), which does not allow intervals to be ordered between a and b.

Note:

Unless a noOverlap constraint is applied to the sequence variable, the order of intervals in a sequence does not necessarily correspond to the order of the intervals in time.
This constraint cannot be used in a meta-constraint.