/// <summary>
/// Expand a multiplication expression.
/// </summary>
/// <param name="f"></param>
/// <param name="x"></param>
/// <returns></returns>
private static Expression ExpandMultiply(Expression f, Expression x)
{
// If the denominator is multiplication, expand partial fractions.
if (!ReferenceEquals(x, null))
{
Expression d = Product.Denominator(f).Factor(x);
if (d is Product)
{
return(ExpandPartialFractions(Product.Numerator(f), (Product)d, x));
}
}
// If f contains an add expression, distribute it.
if (Product.TermsOf(f).Any(i => i is Sum))
{
Expression e = 1;
foreach (Expression i in Product.TermsOf(f))
{
e = Distribute(i.Expand(x), e);
}
return(e);
}
return(f);
}
protected override PrettyString VisitProduct(Product M)
{
Expression N = Product.Numerator(M);
Expression D = Product.Denominator(M);
bool negative = false;
if (N is Product && IsNegative(N))
{
negative = !negative;
N = -N;
}
if (D is Product && IsNegative(D))
{
negative = !negative;
D = -D;
}
if (!D.Equals(1))
{
return(PrettyString.ConcatColumns(negative ? "- " : "", VisitDivide(N, D)));
}
else if (N is Product)
{
return(PrettyString.ConcatColumns(negative ? "-" : "", UnSplit(Product.TermsOf(N), "*")));
}
else
{
return(PrettyString.ConcatColumns(negative ? "-" : "", Visit(N)));
}
}
protected override string VisitProduct(Product M)
{
int pr = Parser.Precedence(Operator.Multiply);
Expression N = Product.Numerator(M);
string minus = "";
if (IsNegative(N))
{
minus = "-";
N = -N;
}
string n = String.Join(" ", Product.TermsOf(N).Select(i => Visit(i, pr)));
string d = String.Join(" ", Product.TermsOf(Product.Denominator(M)).Select(i => Visit(i, pr)));
if (d != "1")
{
return(minus + Frac(n, d));
}
else
{
return(minus + n);
}
}
