private AstItem ReadExpression(TokenIterator tokens, List <TokenKind> terminators)
{
var expTokens = new List <Token>();
if (terminators == null)
{
expTokens.AddRange(tokens.ToList());
}
else
{
var inArray = false;
var tok = tokens.Current();
while (tok != null)
{
if (!inArray && terminators.Contains(tok.Kind))
{
break;
}
if (tok.Kind == TokenKind.SquareBracketOpen)
{
inArray = true;
}
if (tok.Kind == TokenKind.SquareBracketClose)
{
inArray = false;
}
expTokens.Add(tok);
tokens.Step();
tok = tokens.Current();
}
}
if (expTokens.Count == 0)
{
throw new Exception("Expected expression, found " + tokens.Current());
}
AstItem result = null;
var tokenIter = new TokenIterator(expTokens);
if (expTokens.Count == 1)
{
//Single immediate, vector or variable
result = ReadSingleAstItem(tokenIter);
}
else
{
var token = tokenIter.Current();
var next = tokenIter.Next();
if (token.Kind == TokenKind.New)
{
result = ReadNewPointer(tokenIter);
}
else
{
//Math Expression
var expItemsInfix = new List <AstItem>();
var expectOperand = true;
while (token != null)
{
switch (token.Kind)
{
case TokenKind.Word:
case TokenKind.Number:
case TokenKind.True:
case TokenKind.False:
case TokenKind.VectorConstructor:
case TokenKind.Char:
case TokenKind.String:
case TokenKind.SquareBracketOpen:
var operandItem = ReadSingleAstItem(tokenIter);
expItemsInfix.Add(operandItem);
expectOperand = false; //Next we want an operator
break;
case TokenKind.RoundBracketOpen:
case TokenKind.RoundBracketClose:
expItemsInfix.Add(AstItem.AsOperator(ParseOperator(token.Value)));
break;
case TokenKind.ExpressionOperator:
if (expectOperand)
{
expItemsInfix.Add(AstItem.AsUnaryOperator(ParseUnaryOperator(token.Value)));
}
else
{
expItemsInfix.Add(AstItem.AsOperator(ParseOperator(token.Value)));
expectOperand = true; //Next we want an operand
}
break;
default:
throw new Exception("Unexpected expression token: " + token);
}
tokenIter.Step();
token = tokenIter.Current();
}
//Convert to postfix
if (expItemsInfix.Count > 1)
{
result = InfixToPostfix(expItemsInfix);
}
else
{
result = expItemsInfix[0];
}
}
}
return(result);
}