/// <summary>
/// Parses a prototype
/// </summary>
/// <returns>A prototype syntax tree</returns>
private PrototypeSyntaxTree ParsePrototype()
{
int kind = 0;
int binaryPrecedence = 30;
string funcName = "";
CharacterToken charToken = null;
IdentifierToken identToken = null;
switch (this.currentToken.Type)
{
default:
throw new ParserException("Expected function name in prototype");
case TokenType.Identifier:
funcName = ((IdentifierToken)this.currentToken).Value;
kind = 0;
this.NextToken(); //Consume the func name
break;
case TokenType.Binary:
this.NextToken();
charToken = this.currentToken as CharacterToken;
if (charToken == null)
{
throw new ParserException("Expected binary operator");
}
funcName = "binary" + charToken.Value;
kind = 2;
this.NextToken();
//Read the precedence
NumberToken numToken = this.currentToken as NumberToken;
if (numToken != null)
{
if (numToken.Value < 1 || numToken.Value > 100)
{
throw new ParserException("Invalid precedecnce: must be in the range: 1..100");
}
binaryPrecedence = (int)numToken.Value;
this.NextToken();
}
else
{
throw new ParserException("Expected a number");
}
break;
case TokenType.Unary:
this.NextToken();
charToken = this.currentToken as CharacterToken;
if (charToken == null)
{
throw new ParserException("Expected unary operator");
}
funcName = "unary" + charToken.Value;
kind = 1;
this.NextToken();
break;
}
charToken = this.currentToken as CharacterToken;
if ((charToken != null && charToken.Value != '(') || charToken == null)
{
throw new ParserException("Expected '(' in prototype");
}
//Read the arguments
List<string> args = new List<string>();
while (true)
{
this.NextToken();
identToken = this.currentToken as IdentifierToken;
if (identToken != null)
{
args.Add(identToken.Value);
}
else
{
break;
}
}
charToken = this.currentToken as CharacterToken;
if ((charToken != null && charToken.Value != ')') || charToken == null)
{
throw new ParserException("Expected ')' in prototype");
}
this.NextToken(); //Consume the )
//Verify the arguments is the same as the operator
if (kind != 0 && args.Count != kind)
{
throw new ParserException("Invalid number of operands for operator");
}
return new PrototypeSyntaxTree(funcName, args, kind != 0, binaryPrecedence);
}
/// <summary>
/// Parses a number expression
/// </summary>
/// <returns>An number syntax tree</returns>
private ExpressionSyntaxTree ParseNumberExpression()
{
NumberToken numToken = (NumberToken)this.currentToken;
this.NextToken(); //Consume the number
return new NumberExpressionSyntaxTree(numToken.Value);
}