Class: IntStepFunction

Integer step function.

Integer step function is a piecewise constant function defined on integer values in range IntVarMin to IntVarMax. It is defined by an array of points $[[x_0, y_0], [x_1, y_1],\dots , [x_n, y_n]]$ where $x_i$ and $y_i$ are integer values. The array must be sorted by $x_i$ in ascending order and values $x_i$ must be unique. The function is defined as follows:

• $f(x) = 0$ for $x < x_0$,
• $f(x) = y_i$ for $x_i \leq x < x_{i+1}$
• $f(x) = y_n$ for $x \geq x_n$.

Step functions can be used the following ways:

• Function Model.stepFunctionEval evaluates the function at the given point (given as IntExpr).
• Function Model.stepFunctionSum computes a sum (integral) of the function over an IntervalVar.
• Constraints Model.forbidStart and Model.forbidEnd forbid the start/end of an IntervalVar to be in a zero-value interval of the function.
• Constraint Model.forbidExtent forbids the extent of an IntervalVar to be in a zero-value interval of the function.

Extends

• ModelNode

Methods

getName()

getName(): undefined | string

Returns the name assigned to the node.

Returns

undefined | string

Inherited from

ModelNode . getName

---

setName()

setName(name: string): this

Assigns a name to the node.

Parameters

Parameter	Type	Description
name	string	Named to be assigned.

Returns

this

The node itself so it can be used in chained expression.

Inherited from

ModelNode . setName

Remarks

Assigning a name is optional. However is useful for debugging because variable names appear in the development traces. It is also useful for exporting the model to a file (see problem2json).

Example

let model = new CP.Model();
let x = model.intervalVar({ length: 10 }).setName("x");
// The line above is equivalent to:
//   let x = model.intervalVar({ length: 10, name:"x" });
let endOfX = model.endOf(x).setName("endOfX");
let result = await CP.solve(model);

---

stepFunctionEval()

stepFunctionEval(arg: number | IntExpr): IntExpr

Evaluates the step function at a given point.

Parameters

Parameter	Type
arg	number | IntExpr

Returns

IntExpr

Remarks

The result is the value of the step function at the point arg. If the value of arg is absent then the result is also absent.

By constraining the returned value, it is possible to limit arg to be only within certain segments of the segmented function. In particular, functions Model.forbidStart and Model.forbidEnd work that way.

See

• Model.stepFunctionEval for the equivalent function on Model.
• Model.forbidStart, Model.forbidEnd are convenience functions built on top of stepFunctionEval.

---

stepFunctionSum()

stepFunctionSum(interval: IntervalVar): IntExpr

Computes sum of values of the step function over the interval interval.

Parameters

Parameter	Type
interval	IntervalVar

Returns

IntExpr

Remarks

The sum is computed over all points in range interval.start() .. interval.end()-1. That is, the sum includes the function value at the start time, but not the value at the end time. If the interval variable has zero length then the result is 0. If the interval variable is absent then the result is absent.

Requirement: The step function func must be non-negative.

See

Model.stepFunctionSum for the equivalent function on Model.