// _parseExpr parses an expression from the Lexer passed in.
//
private SymplExpr ParseExprAux(Lexer lexer)
{
Token token = lexer.GetToken();
SymplExpr res = null;
if (token == SyntaxToken.EOF)
{
throw new SymplParseException(
"Unexpected EOF encountered while parsing expression.");
}
if (token == SyntaxToken.Quote)
{
lexer.PutToken(token);
res = ParseQuoteExpr(lexer);
}
else if (token == SyntaxToken.Paren)
{
lexer.PutToken(token);
res = ParseForm(lexer);
}
else if (token is IdOrKeywordToken)
{
// If we encounter literal kwd constants, they get turned into ID
// Exprs. Code that accepts Id Exprs, needs to check if the token is
// kwd or not when it matters.
if ((token is KeywordToken) && !(token == KeywordToken.Nil) &&
!(token == KeywordToken.True) && !(token == KeywordToken.False))
{
throw new InvalidCastException("Keyword cannot be an expression");
}
else
{
res = new SymplIdExpr((IdOrKeywordToken)token);
}
}
else if (token is LiteralToken)
{
res = new SymplLiteralExpr(((LiteralToken)token).Value);
}
// check for dotted expr
if (res != null)
{
Token next = lexer.GetToken();
lexer.PutToken(next);
if (next == SyntaxToken.Dot)
{
return(ParseDottedExpr(lexer, res));
}
else
{
return(res);
}
}
throw new SymplParseException(
"Unexpected token when expecting " +
"beginning of expression -- " + token.ToString() + " ... " +
lexer.GetToken().ToString() + lexer.GetToken().ToString() +
lexer.GetToken().ToString() + lexer.GetToken().ToString());
}
// _parseExpr parses an expression from the Lexer passed in.
//
private SymplExpr ParseExprAux(Lexer lexer) {
Token token = lexer.GetToken();
SymplExpr res = null;
if (token == SyntaxToken.EOF) {
throw new SymplParseException(
"Unexpected EOF encountered while parsing expression.");
}
if (token == SyntaxToken.Quote) {
lexer.PutToken(token);
res = ParseQuoteExpr(lexer);
} else if (token == SyntaxToken.Paren) {
lexer.PutToken(token);
res = ParseForm(lexer);
} else if (token is IdOrKeywordToken) {
// If we encounter literal kwd constants, they get turned into ID
// Exprs. Code that accepts Id Exprs, needs to check if the token is
// kwd or not when it matters.
if ((token is KeywordToken) && !(token == KeywordToken.Nil) &&
!(token == KeywordToken.True) && !(token == KeywordToken.False)) {
throw new InvalidCastException("Keyword cannot be an expression");
} else {
res = new SymplIdExpr((IdOrKeywordToken)token);
}
} else if (token is LiteralToken) {
res = new SymplLiteralExpr(((LiteralToken)token).Value);
}
// check for dotted expr
if (res != null) {
Token next = lexer.GetToken();
lexer.PutToken(next);
if (next == SyntaxToken.Dot) {
return ParseDottedExpr(lexer, res);
} else {
return res;
}
}
throw new SymplParseException(
"Unexpected token when expecting " +
"beginning of expression -- " + token.ToString() + " ... " +
lexer.GetToken().ToString() + lexer.GetToken().ToString() +
lexer.GetToken().ToString() + lexer.GetToken().ToString());
}