private static FSharpFunc <CharStream <Unit>, Reply <double> > MathFunc(FSharpFunc <CharStream <Unit>, Reply <double> > term, string key, Func <double, double> func)
{
var noParenthesis = Pipe(StringP(key).And(WS), term, (_, d) => func(d));
var withParenthesis = Pipe(StringP(key).And(WS), CharP('(').And(WS), term.And(WS), CharP(')'), (_, pl, d, pr) => func(d));
return(noParenthesis.Or(withParenthesis));
}
