/*************************/
/*
* (* The grammar assumes any amount of whitespaces between each token *)
*
* digit = ? 0-9 ?;
* binaryDigit = ? 0-1 ? ;
* octalDigit = ? 0-7 ? ;
* hexDigit = ? 0-9A-F ? ;
* letter = ? a-zA-Z ? ;
*
* identifier = ( "_" | letter ) { "_" | letter | digit } ;
* functionName = identifier ;
* constant = identifier ;
*
* number = digit { digit } [ "." digit { digit } ] ;
* binaryNumber = "0b" binaryNumber { binaryNumber } ;
* octalNumber = "0o" octalDigit { octalDigit } ;
* hexNumber = "0x" hexDigit { hexDigit } ;
*
* functionArguments = expr { "," expr } ;
* functionCall = functionName "(" [ functionArguments ] ")" ;
* factorBase = number | "(" expr ")" | functionCall | constant | binaryNumber | octalNumber | hexNumber;
* factor = [ "-" | "~" ] factorBase { "^" factor } [ "!" ];
* term = factor { ( "*" | "/" | "%" | "&" | "@" | "<<" | ">>" ) factor } ;
* expr = term { ( "+" | "-" | "|" ) term } (* | identifier "=" term *) ;
*
*/
ParseTreeNode Expr(bool expectParenthesis = false)
{
ParseTreeNode node = new ParseTreeNode();
if (tokens.HasNext())
{
node.Left = Term();
}
else
{
return(null);
}
if (tokens.HasNext() && (tokens.PeekForward().TokenType == TokenIdentifier.TokenType.PlussOperator ||
tokens.PeekForward().TokenType == TokenIdentifier.TokenType.MinusOperator ||
tokens.PeekForward().TokenType == TokenIdentifier.TokenType.OrOperator))
{
node.Token = tokens.Forward();
node.Right = Term();
while (tokens.HasNext() && (tokens.PeekForward().TokenType == TokenIdentifier.TokenType.PlussOperator ||
tokens.PeekForward().TokenType == TokenIdentifier.TokenType.MinusOperator ||
tokens.PeekForward().TokenType == TokenIdentifier.TokenType.OrOperator))
{
ParseTreeNode newNode = new ParseTreeNode();
newNode.Token = tokens.Forward();
newNode.Left = node;
newNode.Right = Term();
node = newNode;
}
}
if (expectParenthesis && (!tokens.HasNext() || tokens.PeekForward().TokenType != TokenIdentifier.TokenType.RightParenthesis))
{
throw new Exception("Syntax error: Expecting ')' at token " + tokens.Position);
}
else if (expectParenthesis && tokens.HasNext() && tokens.PeekForward().TokenType == TokenIdentifier.TokenType.RightParenthesis)
{
tokens.Forward();
}
if (node.Right == null)
{
node = node.Left;
}
return(node);
}
