Class: IntStepFunction

Piecewise-constant function mapping time to integers, used for costs and availability windows.

Remarks

Integer step function.

Integer step function is a piecewise constant function defined on integer values in range IntVarMin to IntVarMax. The function can be created by Model.stepFunction.

Step functions can be used in the following ways:

• Function Model.eval evaluates the function at the given point (given as IntExpr).
• Function Model.integral 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

• ModelElement

Accessors

name

Get Signature

get name(): string | undefined

The name assigned to this model element.

Remarks

The name is optional and primarily useful for debugging purposes. When set, it helps identify the element in solver logs, error messages, and when inspecting solutions.

Names can be assigned to any model element including variables, expressions, and constraints.

Example

import * as CP from "optalcp";

const model = new CP.Model();

// Name a variable at creation
const task = model.intervalVar({ length: 10, name: "assembly" });

// Or set name later
const x = model.intVar({ min: 0, max: 100 });
x.name = "quantity";

console.log(task.name);  // "assembly"
console.log(x.name);     // "quantity"

Returns

string | undefined

Set Signature

set name(value: string): void

Parameters

Parameter	Type
value	string

Returns

void

Inherited from

ModelElement.name

Constructors

Constructor

new IntStepFunction(): IntStepFunction

Returns

IntStepFunction

Inherited from

ModelElement.constructor

Methods

eval()

eval(arg: number | IntExpr): IntExpr

Evaluates the step function at a given point.

Parameters

Parameter	Type	Description
arg	number | IntExpr	The point at which to evaluate the step function.

Returns

IntExpr

The resulting integer expression

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

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integral()

integral(interval: IntervalVar): IntExpr

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

Parameters

Parameter	Type	Description
interval	IntervalVar	The interval variable.

Returns

IntExpr

The resulting integer expression

Remarks

The sum is computed over all integer time points from interval.start() to interval.end()-1 inclusive. In other words, the sum includes the function value at the start time but excludes the value at the end time (half-open interval). 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.integral for the equivalent function on Model.