public CasExpr Add(CasExpr expr1, CasExpr expr2)
{
if (expr1.Poly2.PolyEquals(expr2.Poly2))
{
return(new CasExpr(CasPolynomial.PolySum(expr1.Poly1, expr2.Poly1), expr2.Poly2));
}
else
{
var p1 = CasPolynomial.PolyProd(expr1.Poly1, expr2.Poly2);
var p2 = CasPolynomial.PolyProd(expr1.Poly2, expr2.Poly1);
var num = CasPolynomial.PolySum(p1, p2);
var denom = CasPolynomial.PolyProd(expr1.Poly2, expr2.Poly2);
return(new CasExpr(num, denom));
}
}
// Result is null if solver fails
public Tuple <CasExpr, CasVar> Solve(CasExpr expr, CasVar forV)
{
if (expr.Poly1.ContainsVar(forV) && expr.Poly2.ContainsVar(forV))
{
return(null);
}
if (!expr.Poly1.ContainsVar(forV) && !expr.Poly2.ContainsVar(forV))
{
return(null);
}
if (expr.Poly1.ContainsVar(forV) && !expr.Poly2.ContainsVar(forV))
{
List <CasTerm> zeroTerms = new List <CasTerm>();
List <CasTerm> oneTerms = new List <CasTerm>();
foreach (var t in expr.Poly1.Terms)
{
if (!t.Variables.ContainsKey(forV))
{
zeroTerms.Add(t);
}
else if (t.Variables[forV] == 1)
{
oneTerms.Add(t);
}
else
{
return(null);
}
}
if (oneTerms.Count == 0)
{
return(null);
}
CasPolynomial polyZeros = new CasPolynomial();
CasPolynomial polyOnes = new CasPolynomial();
foreach (var t in zeroTerms)
{
polyZeros.Terms.Add(t.CopyWithCoefficient(-1 * t.Coefficient));
}
foreach (var t in oneTerms)
{
polyOnes.Terms.Add(t.CopyWithCoefficient(t.Coefficient));
t.Variables.Remove(forV);
}
var newVar = NewVar();
var newTerm = new CasTerm(1);
newTerm.Variables[newVar] = 1;
polyZeros.Terms.Add(newTerm);
var resExpr = new CasExpr(CasPolynomial.PolyProd(polyZeros, expr.Poly2), polyOnes);
return(new Tuple <CasExpr, CasVar>(resExpr, newVar));
}
else
{
List <CasTerm> zeroTerms = new List <CasTerm>();
List <CasTerm> oneTerms = new List <CasTerm>();
foreach (var t in expr.Poly2.Terms)
{
if (!t.Variables.ContainsKey(forV))
{
zeroTerms.Add(t);
}
else if (t.Variables[forV] == 1)
{
oneTerms.Add(t);
}
else
{
return(null);
}
}
if (oneTerms.Count == 0)
{
return(null);
}
CasPolynomial polyZeros = new CasPolynomial();
CasPolynomial polyOnes = new CasPolynomial();
var newVar = NewVar();
foreach (var t in zeroTerms)
{
polyZeros.Terms.Add(t.CopyWithCoefficient(-1 * t.Coefficient));
t.Variables[newVar] = 1;
}
foreach (var t in oneTerms)
{
polyOnes.Terms.Add(t.CopyWithCoefficient(t.Coefficient));
t.Variables.Remove(forV);
t.Variables[newVar] = 1;
}
var resExpr = new CasExpr(CasPolynomial.PolySum(polyZeros, expr.Poly2), polyOnes);
return(new Tuple <CasExpr, CasVar>(resExpr, newVar));
}
}