protected Expression ProductRule(Expression L, IEnumerable <Expression> R)
{
if (R.Empty())
{
return(Visit(L));
}
bool Lx = L.DependsOn(x);
bool Rx = R.DependsOn(x);
if (Lx && Rx)
{
// Product rule.
return(Sum.New(
Product.New(new Expression[] { Visit(L) }.Concat(R)),
Product.New(L, ProductRule(R.First(), R.Skip(1)))).Evaluate());
}
else if (!Lx)
{
// L is constant w.r.t. x.
return(Product.New(L, ProductRule(R.First(), R.Skip(1))).Evaluate());
}
else
{
// R is constant w.r.t. x.
return(Product.New(R.Append(Visit(L))).Evaluate());
}
}
public override Expression Visit(Expression E)
{
if (!E.DependsOn(t))
{
return(E / s);
}
return(base.Visit(E));
}
protected override Expression VisitUnknown(Expression E)
{
if (E.Equals(x))
{
return(1);
}
else if (E.DependsOn(x))
{
return(rules.Transform(Call.D(E, x)));
}
else
{
return(0);
}
}
public override Expression Visit(Expression E)
{
if (x.Equals(E))
{
return(1);
}
else if (!E.DependsOn(x))
{
return(0);
}
else
{
return(base.Visit(E));
}
}
protected override Expression VisitPower(Power P)
{
Expression f = P.Left;
Expression g = P.Right;
if (g.DependsOn(x))
{
// f(x)^g(x)
return(Product.New(P,
Sum.New(
Product.New(Visit(f), Binary.Divide(g, f)),
Product.New(Visit(g), Call.Ln(f)))).Evaluate());
}
else
{
// f(x)^g
return(Product.New(
g,
Power.New(f, Binary.Subtract(g, 1)),
Visit(f)).Evaluate());
}
}
private List <Arrow> Solve(IList <Expression> x)
{
List <Arrow> solutions = new List <Arrow>();
for (int i = Math.Min(x.Count, equations.Count) - 1, _j = x.Count - 1; _j >= 0; --_j)
{
Expression j = x[_j];
// While we still haven't reached a pivot row...
while (i >= 0 && x.Take(_j).All(j2 => equations[i][j2].EqualsZero()))
{
if (!equations[i][j].EqualsZero())
{
// Solve this row for the pivot.
Expression s = equations[i].Solve(j);
if (!s.DependsOn(x))
{
solutions.Add(Arrow.New(j, s));
// Remove the equation and unknown.
equations.RemoveAt(i--);
x.RemoveAt(_j);
if (!ReferenceEquals(x, unknowns))
{
unknowns.Remove(j);
}
}
break;
}
else
{
--i;
}
}
}
return(solutions);
}
public static Expression DependsOn(Expression f, Expression x)
{
return(Constant.New(f.DependsOn(x)));
}
protected override bool IsConstant(Expression x)
{
return(!x.DependsOn(t));
}