operations_research::sat::LinearExpr Class Reference

#include <cp_model.h>

Public Member Functions
	LinearExpr ()=default
	Creates an empty linear expression with value zero.
	LinearExpr (BoolVar var)
	NOLINTBEGIN(google-explicit-constructor)
	LinearExpr (IntVar var)
	Constructs a linear expression from an integer variable.
	LinearExpr (int64_t constant)
	Constructs a constant linear expression.
LinearExpr &	operator+= (const LinearExpr &other)
	Operators.
LinearExpr &	operator-= (const LinearExpr &other)
LinearExpr &	operator*= (int64_t factor)
const std::vector< int > &	variables () const
	Returns the vector of variable indices.
const std::vector< int64_t > &	coefficients () const
	Returns the vector of coefficients.
bool	IsConstant () const
	Returns true if the expression has no variables.
int64_t	constant () const
	Returns the constant term.
std::string	DebugString (const CpModelProto *proto=nullptr) const

Static Public Member Functions
static LinearExpr	Sum (absl::Span< const IntVar > vars)
	NOLINTEND(google-explicit-constructor)
static LinearExpr	Sum (absl::Span< const BoolVar > vars)
	Constructs the sum of a list of Boolean variables.
static LinearExpr	WeightedSum (absl::Span< const IntVar > vars, absl::Span< const int64_t > coeffs)
	Constructs the scalar product of variables and coefficients.
static LinearExpr	WeightedSum (absl::Span< const BoolVar > vars, absl::Span< const int64_t > coeffs)
	Constructs the scalar product of Boolean variables and coefficients.
static LinearExpr	Term (IntVar var, int64_t coefficient)
	Constructs var * coefficient.
static LinearExpr	Term (BoolVar var, int64_t coefficient)
	Constructs bool * coefficient.
static LinearExpr	FromProto (const LinearExpressionProto &proto)
	Constructs a linear expr from its proto representation.

Detailed Description

A dedicated container for linear expressions.

With the use of implicit constructors, it can accept integer values, Boolean and Integer variables. Note that Not(x) will be silently transformed into 1 - x when added to the linear expression. It also support operator overloads to construct the linear expression naturally.

Furthermore, static methods allow to construct a linear expression from sums or scalar products.

Usage:

CpModelBuilder cp_model;
IntVar x = model.NewIntVar({0, 10}).WithName("x");
IntVar y = model.NewIntVar({0, 10}).WithName("y");
BoolVar b = model.NewBoolVar().WithName("b");
BoolVar c = model.NewBoolVar().WithName("c");
LinearExpr e1(x);  // Or e1 = x.
LinearExpr e2 = x + y + 5;
LinearExpr e3 = 2 * x - y;
LinearExpr e4 = b;
LinearExpr e5 = b.Not();  // 1 - b.
std::vector<BoolVar> bools = {b, Not(c)};
LinearExpr e6 = LinearExpr::Sum(bools);   // b + 1 - c;
LinearExpr e7 = -3 * b + Not(c);  // -3 * b + 1 - c;

This can be used implicitly in some of the CpModelBuilder methods.

cp_model.AddGreaterThan(x, 5);
cp_model.AddEquality(x, y + 5);

Definition at line 246 of file cp_model.h.

Constructor & Destructor Documentation

LinearExpr() [1/4]

operations_research::sat::LinearExpr::LinearExpr ( )

default

Creates an empty linear expression with value zero.

LinearExpr() [2/4]

operations_research::sat::LinearExpr::LinearExpr

(

BoolVar

var

)

NOLINTBEGIN(google-explicit-constructor)

Constructs a linear expression from a Boolean variable. It deals with logical negation correctly.

We add 1 - var instead.

Definition at line 176 of file cp_model.cc.

LinearExpr() [3/4]

operations_research::sat::LinearExpr::LinearExpr

(

IntVar

var

)

Constructs a linear expression from an integer variable.

Definition at line 190 of file cp_model.cc.

LinearExpr() [4/4]

operations_research::sat::LinearExpr::LinearExpr

(

int64_t

constant

)

Constructs a constant linear expression.

Definition at line 196 of file cp_model.cc.

Member Function Documentation

coefficients()

const std::vector< int64_t > & operations_research::sat::LinearExpr::coefficients ( ) const

inline

Returns the vector of coefficients.

Definition at line 297 of file cp_model.h.

constant()

int64_t operations_research::sat::LinearExpr::constant ( ) const

inline

Returns the constant term.

Definition at line 303 of file cp_model.h.

DebugString()

std::string operations_research::sat::LinearExpr::DebugString

(

const CpModelProto *

proto = nullptr

)

const

Debug string. If the CpModelBuilder is passed, the string will include variable names and domains. Otherwise, you will get a shorter string with only variable indices.

Definition at line 280 of file cp_model.cc.

FromProto()

LinearExpr operations_research::sat::LinearExpr::FromProto ( const LinearExpressionProto & proto )

static

Constructs a linear expr from its proto representation.

Definition at line 198 of file cp_model.cc.

IsConstant()

bool operations_research::sat::LinearExpr::IsConstant ( ) const

inline

Returns true if the expression has no variables.

Definition at line 300 of file cp_model.h.

operator*=()

LinearExpr & operations_research::sat::LinearExpr::operator*=

(

int64_t

factor

)

Definition at line 274 of file cp_model.cc.

operator+=()

LinearExpr & operations_research::sat::LinearExpr::operator+=

(

const LinearExpr &

other

)

Operators.

Definition at line 255 of file cp_model.cc.

operator-=()

LinearExpr & operations_research::sat::LinearExpr::operator-=

(

const LinearExpr &

other

)

Definition at line 264 of file cp_model.cc.

Sum() [1/2]

LinearExpr operations_research::sat::LinearExpr::Sum ( absl::Span< const BoolVar > vars )

static

Constructs the sum of a list of Boolean variables.

Definition at line 215 of file cp_model.cc.

Sum() [2/2]

LinearExpr operations_research::sat::LinearExpr::Sum ( absl::Span< const IntVar > vars )

static

NOLINTEND(google-explicit-constructor)

Constructs the sum of a list of variables.

Definition at line 207 of file cp_model.cc.

Term() [1/2]

LinearExpr operations_research::sat::LinearExpr::Term ( BoolVar var, int64_t coefficient )

static

Constructs bool * coefficient.

Definition at line 249 of file cp_model.cc.

Term() [2/2]

LinearExpr operations_research::sat::LinearExpr::Term ( IntVar var, int64_t coefficient )

static

Constructs var * coefficient.

Definition at line 243 of file cp_model.cc.

variables()

const std::vector< int > & operations_research::sat::LinearExpr::variables ( ) const

inline

Returns the vector of variable indices.

Definition at line 294 of file cp_model.h.

WeightedSum() [1/2]

LinearExpr operations_research::sat::LinearExpr::WeightedSum ( absl::Span< const BoolVar > vars, absl::Span< const int64_t > coeffs )

static

Constructs the scalar product of Boolean variables and coefficients.

Definition at line 233 of file cp_model.cc.

WeightedSum() [2/2]

LinearExpr operations_research::sat::LinearExpr::WeightedSum ( absl::Span< const IntVar > vars, absl::Span< const int64_t > coeffs )

static

Constructs the scalar product of variables and coefficients.

Definition at line 223 of file cp_model.cc.

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The documentation for this class was generated from the following files:

• ortools/sat/cp_model.h
• ortools/sat/cp_model.cc