Added the Substitute() and SubstituteAccordingTo() methods for constraints to simplify some operations

Author: Kwesi Rutledge

symbolic/constraint.go

@@ -13,6 +13,8 @@ type Constraint interface {
 	ConstrSense() ConstrSense
 	Check() error
 	IsLinear() bool
+	Substitute(vIn Variable, seIn ScalarExpression) Constraint
+	SubstituteAccordingTo(subMap map[Variable]Expression) Constraint
 }
 
 func IsConstraint(c interface{}) bool {

symbolic/matrix_constraint.go

@@ -2,6 +2,7 @@ package symbolic
 
 import (
 	"fmt"
+
 	"github.com/MatProGo-dev/SymbolicMath.go/smErrors"
 )
 
@@ -145,3 +146,48 @@ Description:
 func (mc MatrixConstraint) IsLinear() bool {
 	return IsLinear(mc.RightHandSide) && IsLinear(mc.LeftHandSide)
 }
+
+/*
+Substitute
+Description:
+
+	Substitutes the variable vIn with the scalar expression seIn
+*/
+func (mc MatrixConstraint) Substitute(vIn Variable, seIn ScalarExpression) Constraint {
+	// Check that the constraint is well formed.
+	err := mc.Check()
+	if err != nil {
+		panic(err)
+	}
+
+	// Substitute the variable in the left hand side
+	newLHS := mc.LeftHandSide.Substitute(vIn, seIn).(MatrixExpression)
+
+	// Substitute the variable in the right hand side
+	newRHS := mc.RightHandSide.Substitute(vIn, seIn).(MatrixExpression)
+
+	return MatrixConstraint{newLHS, newRHS, mc.Sense}
+}
+
+/*
+SubstituteAccordingTo
+Description:
+
+	Substitutes the variables in the map with the corresponding expressions
+	in the given scalar constraint.
+*/
+func (mc MatrixConstraint) SubstituteAccordingTo(subMap map[Variable]Expression) Constraint {
+	// Check that the constraint is well formed.
+	err := mc.Check()
+	if err != nil {
+		panic(err)
+	}
+
+	// Substitute the variable in the left hand side
+	newLHS := mc.LeftHandSide.SubstituteAccordingTo(subMap).(MatrixExpression)
+
+	// Substitute the variable in the right hand side
+	newRHS := mc.RightHandSide.SubstituteAccordingTo(subMap).(MatrixExpression)
+
+	return MatrixConstraint{newLHS, newRHS, mc.Sense}
+}

symbolic/scalar_constraint.go

@@ -208,3 +208,59 @@ func (sc ScalarConstraint) LinearEqualityConstraintRepresentation(wrt ...[]Varia
 	// Return
 	return C, d
 }
+
+/*
+Substitute
+Description:
+
+	Substitutes the variable vIn with the scalar expression seIn in the
+	given scalar constraint.
+*/
+func (sc ScalarConstraint) Substitute(vIn Variable, seIn ScalarExpression) Constraint {
+	// Check that the constraint is well formed.
+	err := sc.Check()
+	if err != nil {
+		panic(err)
+	}
+
+	// Substitute the variable in the left hand side
+	newLHS := sc.LeftHandSide.Substitute(vIn, seIn).(ScalarExpression)
+
+	// Substitute the variable in the right hand side
+	newRHS := sc.RightHandSide.Substitute(vIn, seIn).(ScalarExpression)
+
+	// Return the new constraint
+	return ScalarConstraint{
+		LeftHandSide:  newLHS,
+		RightHandSide: newRHS,
+		Sense:         sc.Sense,
+	}
+}
+
+/*
+SubstituteAccordingTo
+Description:
+
+	Substitutes the variables in the map with the corresponding expressions
+	in the given scalar constraint.
+*/
+func (sc ScalarConstraint) SubstituteAccordingTo(subMap map[Variable]Expression) Constraint {
+	// Check that the constraint is well formed.
+	err := sc.Check()
+	if err != nil {
+		panic(err)
+	}
+
+	// Substitute the variable in the left hand side
+	newLHS := sc.LeftHandSide.SubstituteAccordingTo(subMap).(ScalarExpression)
+
+	// Substitute the variable in the right hand side
+	newRHS := sc.RightHandSide.SubstituteAccordingTo(subMap).(ScalarExpression)
+
+	// Return the new constraint
+	return ScalarConstraint{
+		LeftHandSide:  newLHS,
+		RightHandSide: newRHS,
+		Sense:         sc.Sense,
+	}
+}

symbolic/vector_constraint.go

@@ -257,3 +257,45 @@ func (vc VectorConstraint) LinearEqualityConstraintRepresentation(wrt ...[]Varia
 	// Return the tuple
 	return C, d
 }
+
+/*
+Substitute
+Description:
+
+	Substitutes the variable vIn with the scalar expression seIn in the vector constraint.
+*/
+func (vc VectorConstraint) Substitute(vIn Variable, seIn ScalarExpression) Constraint {
+	// Check that the constraint is well formed.
+	err := vc.Check()
+	if err != nil {
+		panic(err)
+	}
+
+	// Substitute the variable in the left and right hand sides.
+	newLHS := vc.LeftHandSide.Substitute(vIn, seIn).(VectorExpression)
+	newRHS := vc.RightHandSide.Substitute(vIn, seIn).(VectorExpression)
+
+	// Return the new constraint
+	return VectorConstraint{newLHS, newRHS, vc.Sense}
+}
+
+/*
+SubstituteAccordingTo
+Description:
+
+	Substitutes the variables in the map with the corresponding expressions
+*/
+func (vc VectorConstraint) SubstituteAccordingTo(subMap map[Variable]Expression) Constraint {
+	// Check that the constraint is well formed.
+	err := vc.Check()
+	if err != nil {
+		panic(err)
+	}
+
+	// Substitute the variable in the left and right hand sides.
+	newLHS := vc.LeftHandSide.SubstituteAccordingTo(subMap).(VectorExpression)
+	newRHS := vc.RightHandSide.SubstituteAccordingTo(subMap).(VectorExpression)
+
+	// Return the new constraint
+	return VectorConstraint{newLHS, newRHS, vc.Sense}
+}