Function cp::ActivityLength(optionalActivity, absentValue)

# cp::ActivityLength

The function cp::ActivityLength(a,d) returns the length of activity $$a$$ when present and default value $$d$$ when absent.

## Mathematical Formulation

The function cp::ActivityLength(a,d) is equivalent to

$\begin{split}\left\{ \begin{array}{ll} a.\texttt{length} & \textrm{if } a.\texttt{present} \\ d & \textrm{otherwise } \end{array} \right.\end{split}$

This function is typically used in scheduling problems to link activities to other components of the problem.

cp::ActivityLength(
optionalActivity,   ! (input) an expression
absentValue         ! (input) an expression
)


## Arguments

optionalActivity

An expression resulting in an activity. This activity may have the property optional.

absentValue

An expression that results in the value used when activity optionalActivity is absent. This expression cannot involve variables.

## Return Value

This function returns the length of an activity when that activity is present or a specified default value when it is not.

## Example

In the example below, we require that the length of an activity is 36, whether or not it is present. When the length of an activity is fixed, if it is present, then this type of constraint might improve the performance of the CP solver.

Constraint linkShiftActivity {
Definition :  cp::ActivityLength( myAct, 36 ) = 36;
}


Note that the above constraint is automatically generated when the length attribute of activity myAct is specified as 36.