static SimpleMaths()
{
var number = Terminals.Double("Number");
var expression = Nonterminal.Create <double>("Expression");
expression.SetProductions(
number.AsIs(),
expression.Extended().Append("+").Extend(expression).Finish((x1, x2) => x1 + x2),
expression.Extended().Append("-").Extend(expression).Finish((x1, x2) => x1 - x2),
expression.Extended().Append("*").Extend(expression).Finish((x1, x2) => x1 * x2),
expression.Extended().Append("/").Extend(expression).Finish((x1, x2) => x1 / x2),
"-".Appended().Extend(expression).WithPrecedence(out var NEG).Finish(x => - x),
expression.Extended().Append("^").Extend(expression).Finish(Math.Pow),
"(".Appended().Extend(expression).Append(")").AsIs());
var opScope = new OperatorScope(
new LeftAssociative("+", "-"),
new LeftAssociative("*", "/"),
new PrecedenceOnly(NEG),
new RightAssociative("^"));
Designtime = expression.WithOperatorScope(opScope);
Runtime = Designtime.Build();
}