public static TermsBase Create(IEnumerable <TermBase> terms)
{
if (terms == null)
{
throw new ArgumentNullException(nameof(terms));
}
var(constants, ones, variables, ts) = terms.OfType <TermConstant, TermOne, TermVariables, Term>();
var constant = TermConstant.Create(constants.Aggregate((Constant) new ConstantZero(), (c1, c2) => c1 + c2.Coeff) + ConstantWhole.Create(ones.Count()));
var variable = variables.Select(t => (c: (Constant) new ConstantOne(), v: t.Variables)).Concat(ts.Select(t => (c: t.Coeff, v: t.Var))).ToLookup(t => t.v, t => t.c).Select(SumGroup);
var lookup = variable.Concat(new[] { constant });
if (lookup.Count() == 1)
{
return(TermsSingle.Create(lookup.First()));
}
if (lookup.Count() < 1)
{
return(new TermsZero());
}
return(new Terms(lookup));
}
internal static TermsBase Root(Expr @base, BigInteger root) => TermsSingle.Create(TermVariables.Create(VarRootN.Create(@base, root)));
