Added the Substitute() and SubstituteAccordingTo() methods for constr… (#18)

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

* Upgraded the gonum dependency

* Introducing Len() function for vector constraints

* Updating github action to use newer version of Go

* Added tests for ScalarConstraint's Substitute method

* Fixed subtle bug in monomial's substitute according to method

* Introduced string() method to constraint

* Removing debugging statement

* Add in tests for VectorConstraint.Substitute()

* Adding tests for VectorConstraint.SubstituteAccordingTo

* Added small test for ScalarConstraint.String method

* Added tests for MatrixConstraint.Substitute and MatrixConstraint.SubstituteAccordingTo

---------

Co-authored-by: Kwesi Rutledge <kwesir@csail.mit.edu>

Author: kwesiRutledge

.github/workflows/coverage1.yml

@@ -14,7 +14,7 @@ jobs:
     strategy:
       matrix:
         os: [ubuntu-latest, macos-latest, windows-latest]
-        go: [1.19]
+        go: [1.23]
     permissions:
       # Give the default GITHUB_TOKEN write permission to commit and push the
       # added or changed files to the repository.

go.mod

@@ -1,5 +1,7 @@
 module github.com/MatProGo-dev/SymbolicMath.go
 
-go 1.21
+go 1.23.0
 
-require gonum.org/v1/gonum v0.14.0
+toolchain go1.23.8
+
+require gonum.org/v1/gonum v0.16.0

go.sum

@@ -1,4 +1,2 @@
-golang.org/x/exp v0.0.0-20230321023759-10a507213a29 h1:ooxPy7fPvB4kwsA2h+iBNHkAbp/4JxTSwCmvdjEYmug=
-golang.org/x/exp v0.0.0-20230321023759-10a507213a29/go.mod h1:CxIveKay+FTh1D0yPZemJVgC/95VzuuOLq5Qi4xnoYc=
-gonum.org/v1/gonum v0.14.0 h1:2NiG67LD1tEH0D7kM+ps2V+fXmsAnpUeec7n8tcr4S0=
-gonum.org/v1/gonum v0.14.0/go.mod h1:AoWeoz0becf9QMWtE8iWXNXc27fK4fNeHNf/oMejGfU=
+gonum.org/v1/gonum v0.16.0 h1:5+ul4Swaf3ESvrOnidPp4GZbzf0mxVQpDCYUQE7OJfk=
+gonum.org/v1/gonum v0.16.0/go.mod h1:fef3am4MQ93R2HHpKnLk4/Tbh/s0+wqD5nfa6Pnwy4E=

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/monomial.go

@@ -727,11 +727,13 @@ func (m Monomial) SubstituteAccordingTo(subMap map[Variable]Expression) Expressi
 
 	// Algorithm
 	// Create the monomial
-	var out Expression = K(0.0)
+	var out Expression = K(m.Coefficient)
 
 	// Iterate through each variable in the monomial
-	for tempVar, tempExp := range subMap {
-		out = out.Substitute(tempVar, tempExp.(ScalarExpression))
+	for ii, varII := range m.VariableFactors {
+		out = out.Multiply(
+			varII.SubstituteAccordingTo(subMap).Power(m.Exponents[ii]),
+		)
 	}
 
 	// Return

symbolic/scalar_constraint.go

@@ -208,3 +208,76 @@ 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,
+	}
+}
+
+/*
+String
+Description:
+
+	Returns a string representation of the scalar constraint.
+*/
+func (sc ScalarConstraint) String() string {
+	// Check that the constraint is well formed.
+	err := sc.Check()
+	if err != nil {
+		panic(err)
+	}
+
+	// Create the string representation
+	return sc.LeftHandSide.String() + " " + sc.Sense.String() + " " + sc.RightHandSide.String()
+}

symbolic/vector_constraint.go

@@ -257,3 +257,62 @@ 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}
+}
+
+/*
+Len
+Description:
+
+	Returns the length of the vector constraint.
+*/
+func (vc VectorConstraint) Len() int {
+	// Check that the constraint is well formed.
+	err := vc.Check()
+	if err != nil {
+		panic(err)
+	}
+
+	// Return the length of the vector constraint.
+	return vc.LeftHandSide.Len()
+}