private ExpressionList ParseColumnList()
{
//match exp [as <string>](, exp [as <string>])*
ExpressionList l = new ExpressionList();
while (true) {
ParseExpression();
if (_exprs.Count < 1) {
throw new Exception("The base expression is missing.");
}
NamedExpr e = new NamedExpr(null, _exprs.Pop());
if (_tokens.LookAhead().TokenType == TokenType.KW_AS) {
_tokens.Read();
Token t = _tokens.LookAhead();
if (t.TokenType == TokenType.LT_STRING || t.TokenType == TokenType.ID) {
t = _tokens.Read();
}
else {
throw new Exception("The alias must be a string literal.");
}
e.Name = t.Lexeme.ToString();
}
l.Add(e);
//consumes the , delimiter
if (_tokens.LookAhead().TokenType != TokenType.PM_COMMA) { break; }
else {
_tokens.Read();
}
}
return l;
}
private void ParseCastExpr()
{
if (_tokens.LookAhead().TokenType != TokenType.PM_LPAREN) {
throw new Exception("function call syntax error, missing '('");
}
_tokens.Read();
ParseExpression();
if (_exprs.Count < 1) {
throw new Exception("missing the source argument");
}
NamedExpr e = new NamedExpr(null, _exprs.Pop());
if (_tokens.LookAhead().TokenType == TokenType.KW_AS) {
_tokens.Read();
Token t = _tokens.LookAhead();
if (t.TokenType == TokenType.LT_STRING || t.TokenType == TokenType.ID) {
t = _tokens.Read();
}
else {
throw new Exception("The alias must be a string literal.");
}
e.Name = t.Lexeme.ToString();
}
else {
throw new Exception("CAST expression syntax error, missing target type");
}
FuncExpr f = new CastFunction();
f.Arguments = new ExpressionList();
f.Arguments.Add(e);
if (_tokens.LookAhead().TokenType != TokenType.PM_RPAREN) {
throw new Exception("function call syntax error, missing ')'");
}
_tokens.Read();
_exprs.Push(f);
}
