// Atom : Value | LParen Expression RParen
internal static INode Produce(TokenBuffer tokens)
{
var value = Value.Produce(tokens);
if (value != null)
return value;
// HACK
if (tokens.Current is LeftParenthesis)
tokens.SavePosition();
var lParen = tokens.GetTerminal<LeftParenthesis>();
if (lParen == null)
return null;
var expression = Expression.Produce(tokens);
if (expression == null)
{
tokens.RestorePosition();
return null;
}
var rParen = tokens.GetTerminal<RightParenthesis>();
if (rParen == null)
{
throw new ParseException("Missing closing parenthesis");
}
return expression;
}
// ExpRoot (MulDivOp ExpRoot)*
internal static INode Produce(TokenBuffer tokens)
{
var expRoot = ExpRoot.Produce(tokens);
if (expRoot == null)
return null;
tokens.SavePosition();
return BuildSubNodes(expRoot, tokens);
}
// AddSub : MulDiv (AddSubOp MulDiv)*
internal static INode Produce(TokenBuffer tokens)
{
var mulDiv = MulDiv.Produce(tokens);
if (mulDiv == null)
return null;
tokens.SavePosition();
return BuildSubNodes(mulDiv, tokens);
}
// ExpRoot : Unary ExpRootOp ExpRoot | Unary
internal static INode Produce(TokenBuffer tokens)
{
var unary = Unary.Produce(tokens);
if (unary == null)
return null;
tokens.SavePosition();
var expRootOp = ExpRootOp.Produce(tokens);
if (expRootOp == null)
return unary;
var rhs = ExpRoot.Produce(tokens);
if (rhs != null)
return new ExpRoot(unary, expRootOp, rhs);
tokens.RestorePosition();
return null;
}
// Unary : AddSubOp? Atom
internal static INode Produce(TokenBuffer tokens)
{
// HACK
if (tokens.Current is AdditionOperator || tokens.Current is SubtractionOperator)
tokens.SavePosition();
var op = AddSubOp.Produce(tokens);
var atom = Atom.Produce(tokens);
if (atom != null)
{
if (op != null && op.IsMinus)
return new Unary(op, atom);
return atom;
}
tokens.RestorePosition();
return null;
}