private bool ParseLiteralValue(ref ASTNode retn)
{
tokenStream.Save();
// todo if we support bitwise not, add it here
if (tokenStream.Current == ExpressionTokenType.Not && tokenStream.Next == ExpressionTokenType.Boolean)
{
bool value = bool.Parse(tokenStream.Next.value);
retn = ASTNode.BooleanLiteralNode((!value).ToString()).WithLocation(tokenStream.Current);
tokenStream.Advance(2);
return(true);
}
if (tokenStream.Current == ExpressionTokenType.Minus && tokenStream.Next == ExpressionTokenType.Number && (tokenStream.Previous.IsOperator || !tokenStream.HasPrevious))
{
retn = ASTNode.NumericLiteralNode("-" + tokenStream.Next.value).WithLocation(tokenStream.Current);
tokenStream.Advance(2);
return(true);
}
if (tokenStream.Current == ExpressionTokenType.Plus && tokenStream.Next == ExpressionTokenType.Number && (tokenStream.Previous.IsOperator || !tokenStream.HasPrevious))
{
retn = ASTNode.NumericLiteralNode(tokenStream.Next.value).WithLocation(tokenStream.Current);
tokenStream.Advance(2);
return(true);
}
switch (tokenStream.Current.expressionTokenType)
{
case ExpressionTokenType.Null:
retn = ASTNode.NullLiteralNode(tokenStream.Current.value).WithLocation(tokenStream.Current);
break;
case ExpressionTokenType.String:
retn = ASTNode.StringLiteralNode(tokenStream.Current.value).WithLocation(tokenStream.Current);
break;
case ExpressionTokenType.Boolean:
retn = ASTNode.BooleanLiteralNode(tokenStream.Current.value).WithLocation(tokenStream.Current);
break;
case ExpressionTokenType.Number:
retn = ASTNode.NumericLiteralNode(tokenStream.Current.value).WithLocation(tokenStream.Current);
break;
case ExpressionTokenType.Default:
// todo -- allow a type expression a-la default(List<float>);
retn = ASTNode.DefaultLiteralNode(tokenStream.Current.value).WithLocation(tokenStream.Current);
break;
default:
return(false);
}
tokenStream.Advance();
return(true);
}
private ASTNode ParseLoop()
{
while (tokenStream.HasMoreTokens)
{
ASTNode operand = default;
if (ParseExpression(ref operand))
{
if (tokenStream.Current == ExpressionTokenType.Increment)
{
tokenStream.Advance();
expressionStack.Push(ASTNode.UnaryExpressionNode(ASTNodeType.UnaryPostIncrement, operand));
}
else if (tokenStream.Current == ExpressionTokenType.Decrement)
{
tokenStream.Advance();
expressionStack.Push(ASTNode.UnaryExpressionNode(ASTNodeType.UnaryPostDecrement, operand));
}
else
{
expressionStack.Push(operand);
}
continue;
}
if (expressionStack.Count == 0)
{
Abort();
}
if (tokenStream.Current == ExpressionTokenType.QuestionMark && !tokenStream.NextTokenIs(ExpressionTokenType.QuestionMark))
{
while (operatorStack.Count != 0)
{
OperatorNode opNode = operatorStack.Pop();
opNode.right = expressionStack.Pop();
opNode.left = expressionStack.Pop();
expressionStack.Push(opNode);
}
OperatorNode condition = ASTNode.OperatorNode(OperatorType.TernaryCondition);
OperatorNode selection = ASTNode.OperatorNode(OperatorType.TernarySelection);
condition.WithLocation(tokenStream.Previous);
tokenStream.Advance();
int idx = tokenStream.FindMatchingTernaryColon();
if (idx != -1)
{
TokenStream stream = tokenStream.AdvanceAndReturnSubStream(idx);
// parse the left side of the : operator
ExpressionParser parser = new ExpressionParser(stream);
ASTNode leftNode = parser.ParseLoop();
parser.Release();
tokenStream.Advance(); // step over colon
ExpressionParser parserRight = new ExpressionParser(tokenStream);
ASTNode rightNode = parserRight.ParseLoop();
tokenStream.Set(parserRight.tokenStream.CurrentIndex);
parserRight.Release(false);
selection.left = leftNode;
selection.right = rightNode;
condition.left = expressionStack.Pop();
condition.right = selection;
expressionStack.Push(condition);
}
else
{
// read to end use implicit default value for left hand side
ExpressionParser parserLeft = new ExpressionParser(tokenStream);
ASTNode leftNode = parserLeft.ParseLoop();
tokenStream.Set(parserLeft.tokenStream.CurrentIndex);
parserLeft.Release(false);
selection.left = leftNode;
selection.right = ASTNode.DefaultLiteralNode("default");
condition.left = expressionStack.Pop();
condition.right = selection;
expressionStack.Push(condition);
}
continue;
}
OperatorNode op;
if (!ParseOperatorExpression(out op))
{
Abort();
break;
}
while (operatorStack.Count != 0 && op.priority <= operatorStack.Peek().priority)
{
OperatorNode opNode = operatorStack.Pop();
opNode.right = expressionStack.Pop();
opNode.left = expressionStack.Pop();
expressionStack.Push(opNode);
}
operatorStack.Push(op);
}
while (operatorStack.Count != 0)
{
OperatorNode opNode = operatorStack.Pop();
opNode.right = expressionStack.Pop();
opNode.left = expressionStack.Pop();
expressionStack.Push(opNode);
}
if (expressionStack.Count != 1)
{
Abort();
}
return(expressionStack.Pop());
}