LinearExpr

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 241 of file cp_model.h.

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

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

Constructor & Destructor Documentation

LinearExpr() [1/4]

LinearExpr ( )

default

Creates an empty linear expression with value zero.

LinearExpr() [2/4]

LinearExpr

(

BoolVar

var

)

Constructs a linear expression from a Boolean variable.

It deals with logical negation correctly.

Definition at line 175 of file cp_model.cc.

LinearExpr() [3/4]

LinearExpr

(

IntVar

var

)

Constructs a linear expression from an integer variable.

Definition at line 189 of file cp_model.cc.

LinearExpr() [4/4]

LinearExpr

(

int64_t

constant

)

Constructs a constant linear expression.

Definition at line 195 of file cp_model.cc.

Member Function Documentation

coefficients()

const std::vector<int64_t>& coefficients ( ) const

inline

Returns the vector of coefficients.

Definition at line 292 of file cp_model.h.

constant()

int64_t constant ( ) const

inline

Returns the constant term.

Definition at line 298 of file cp_model.h.

DebugString()

std::string 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 279 of file cp_model.cc.

FromProto()

LinearExpr FromProto ( const LinearExpressionProto &  proto )

static

Constructs a linear expr from its proto representation.

Definition at line 197 of file cp_model.cc.

IsConstant()

const bool IsConstant ( ) const

inline

Returns true if the expression has no variables.

Definition at line 295 of file cp_model.h.

operator*=()

LinearExpr & operator*=

(

int64_t

factor

)

Definition at line 273 of file cp_model.cc.

operator+=()

LinearExpr & operator+=

(

const LinearExpr &

other

)

Definition at line 254 of file cp_model.cc.

operator-=()

LinearExpr & operator-=

(

const LinearExpr &

other

)

Definition at line 263 of file cp_model.cc.

Sum() [1/2]

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

static

Constructs the sum of a list of Boolean variables.

Definition at line 214 of file cp_model.cc.

Sum() [2/2]

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

static

Constructs the sum of a list of variables.

Definition at line 206 of file cp_model.cc.

Term() [1/2]

LinearExpr Term ( BoolVar  var, int64_t  coefficient  )

static

Constructs bool * coefficient.

Definition at line 248 of file cp_model.cc.

Term() [2/2]

LinearExpr Term ( IntVar  var, int64_t  coefficient  )

static

Constructs var * coefficient.

Definition at line 242 of file cp_model.cc.

variables()

const std::vector<int>& variables ( ) const

inline

Returns the vector of variable indices.

Definition at line 289 of file cp_model.h.

WeightedSum() [1/2]

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 232 of file cp_model.cc.

WeightedSum() [2/2]

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 222 of file cp_model.cc.

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

• cp_model.h
• cp_model.cc