Every constraint has a strength that determines where it sits in the hierarchy; strong constraints are always satisfied in preference to weaker ones. More...

#include <CeresEngine/Foundation/Constraint/ConstraintStrength.hpp>

Public Member Functions
constexpr	ConstraintStrength (const ConstraintSymbolicWeight &symbolicWeight, const double w)

constexpr	ConstraintStrength (const double a, const double b, const double c, const double w=1.0)
	Construct a strength from three weight factors.

bool	isRequired () const
	Check if this strength signals a required constraint.

const ConstraintSymbolicWeight &	getSymbolicWeight () const
	Get the 3-tuple symbolic weight.

double	getWeight () const
	Get the 3-tuple symbolic weight.

double	getAdjustedWeight () const
	Gets the adjusted weight as a double.

Static Public Attributes
static const ConstraintStrength	required
	Constraints with this strength must be satisfied.

static const ConstraintStrength	strong {1, 0, 0}
	The default strength for edit constraints.

static const ConstraintStrength	medium {0, 1, 0}
	Medium constraint strength.

static const ConstraintStrength	weak {0, 0, 1}
	The default strength for stay constraints.

Private Attributes
ConstraintSymbolicWeight	mSymbolicWeight

double	mWeight = 1.0

Friends
bool	operator== (const ConstraintStrength &lhs, const ConstraintStrength &rhs)

bool	operator!= (const ConstraintStrength &lhs, const ConstraintStrength &rhs)

bool	operator<= (const ConstraintStrength &lhs, const ConstraintStrength &rhs)

bool	operator< (const ConstraintStrength &lhs, const ConstraintStrength &rhs)

bool	operator>= (const ConstraintStrength &lhs, const ConstraintStrength &rhs)

bool	operator> (const ConstraintStrength &lhs, const ConstraintStrength &rhs)

ConstraintStrength	operator* (ConstraintStrength lhs, double w)

Detailed Description

Every constraint has a strength that determines where it sits in the hierarchy; strong constraints are always satisfied in preference to weaker ones.

Since we want to be able to express preferences as well as requirements in the constraint system, we need a specification for how conflicting preferences are to be traded off. In a constraint hierarchy each constraint has a strength. The 'required' strength is special, in that required constraints must be satisfied. The other strengths all label non- required constraints.

A constraint of a given strength completely dominates any constraint with a weaker strength. In the hierarchy theory, a comparator is used to compare different possible solutions to the constraints and select among them. Within this framework a number of variations are possible.

One decision is whether we only compare solutions on a constraint-by-constraint basis (a local comparator), or whether we take some aggregate measure of the unsatisfied constraints of a given strength (a global comparator). A second choice is whether we are concerned only whether a constraint is satisfied or not (a predicate comparator), or whether we also want to know how nearly satisfied it is (a metric comparator).

Constraints whose domain is a metric space, for example the reals, can have an associated error function. The error in satisfying a constraint is zero if and only if the constraint is satisfied, and becomes larger the less nearly satisfied it is. For a given collection of constraints, Cassowary finds a locally-error-better or a weighted-sum-better solution.

Constructor & Destructor Documentation

◆ ConstraintStrength() [1/2]

constexpr CeresEngine::Constraint::ConstraintStrength::ConstraintStrength	(	const ConstraintSymbolicWeight &	symbolicWeight,
		const double	w
	)

inlineconstexpr

◆ ConstraintStrength() [2/2]

constexpr CeresEngine::Constraint::ConstraintStrength::ConstraintStrength	(	const double	a,
		const double	b,
		const double	c,
		const double	w = `1.0`
	)

inlineconstexpr

Construct a strength from three weight factors.

Parameters

a	'Strong' weight
b	'Medium weight
c	'Weak' weight
w	The weight factor.

Member Function Documentation

◆ getAdjustedWeight()

double CeresEngine::Constraint::ConstraintStrength::getAdjustedWeight ( ) const

inline

Gets the adjusted weight as a double.

◆ getSymbolicWeight()

const ConstraintSymbolicWeight & CeresEngine::Constraint::ConstraintStrength::getSymbolicWeight ( ) const

inline

Get the 3-tuple symbolic weight.

◆ getWeight()

double CeresEngine::Constraint::ConstraintStrength::getWeight ( ) const

inline

Get the 3-tuple symbolic weight.

◆ isRequired()

bool CeresEngine::Constraint::ConstraintStrength::isRequired ( ) const

inline

Check if this strength signals a required constraint.

Friends And Related Symbol Documentation

◆ operator!=

bool operator!=	(	const ConstraintStrength &	lhs,
		const ConstraintStrength &	rhs
	)

friend

◆ operator*

ConstraintStrength operator*	(	ConstraintStrength	lhs,
		double	w
	)

friend

◆ operator<

bool operator<	(	const ConstraintStrength &	lhs,
		const ConstraintStrength &	rhs
	)

friend

◆ operator<=

bool operator<=	(	const ConstraintStrength &	lhs,
		const ConstraintStrength &	rhs
	)

friend

◆ operator==

bool operator==	(	const ConstraintStrength &	lhs,
		const ConstraintStrength &	rhs
	)

friend

◆ operator>

bool operator>	(	const ConstraintStrength &	lhs,
		const ConstraintStrength &	rhs
	)

friend

◆ operator>=

bool operator>=	(	const ConstraintStrength &	lhs,
		const ConstraintStrength &	rhs
	)

friend

Member Data Documentation

◆ medium

const ConstraintStrength CeresEngine::Constraint::ConstraintStrength::medium {0, 1, 0}

inlinestatic

Medium constraint strength.

◆ mSymbolicWeight

ConstraintSymbolicWeight CeresEngine::Constraint::ConstraintStrength::mSymbolicWeight

private

◆ mWeight

double CeresEngine::Constraint::ConstraintStrength::mWeight = 1.0

private

◆ required

const ConstraintStrength CeresEngine::Constraint::ConstraintStrength::required

inlinestatic

Initial value:

{
        std::numeric_limits<double>::max(),
        std::numeric_limits<double>::max(),
        std::numeric_limits<double>::max(),
    }

Constraints with this strength must be satisfied.

Used by default for constraints provided by the programmer.

◆ strong

const ConstraintStrength CeresEngine::Constraint::ConstraintStrength::strong {1, 0, 0}

inlinestatic

The default strength for edit constraints.

◆ weak

const ConstraintStrength CeresEngine::Constraint::ConstraintStrength::weak {0, 0, 1}

inlinestatic

The default strength for stay constraints.

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

/Users/Rogiel/Developer/CeresEngine/Engine/Sources/CeresEngine/Foundation/Constraint/ConstraintStrength.hpp

Public Member Functions

Static Public Attributes

Private Attributes

Friends

Detailed Description

Constructor & Destructor Documentation

◆ ConstraintStrength() [1/2]

◆ ConstraintStrength() [2/2]

Member Function Documentation

◆ getAdjustedWeight()

◆ getSymbolicWeight()

◆ getWeight()

◆ isRequired()

Friends And Related Symbol Documentation

◆ operator!=

◆ operator*

◆ operator<

◆ operator<=

◆ operator==

◆ operator>

◆ operator>=

Member Data Documentation

◆ medium

◆ mSymbolicWeight

◆ mWeight

◆ required

◆ strong

◆ weak