public Expression ParseExpression(int precedence = 0)
{
var token = Take();
IPrefixParselet prefix;
IInfixParselet infix;
if (!PrefixParselets.TryGetValue(token.ID, out prefix))
{
throw new RantException(_src, token, "Invalid expression '\{token.Value}'.");
}
var left = prefix.Parse(this, token);
// Break when the next token's precedence is less than or equal to the current precedence
// This will assure that higher precedence operations like multiplication are parsed before lower operations.
while (GetPrecedence() > precedence)
{
token = Take();
if (!InfixParselets.TryGetValue(token.ID, out infix))
{
throw new RantException(_src, token, "Invalid operator '\{token.Value}'.");
}
// Replace the left expression with the next parsed expression.
left = infix.Parse(this, left, token);
}
return(left);
}
/// <summary>
/// Gets the prefix parselet registered to the token type
/// </summary>
/// <param name="tokenClass">Token type to check</param>
/// <returns>Parslet the token type is registered to</returns>
public static IPrefixParselet GetPrefix(TokenType tokenClass)
{
if (PrefixParselets.ContainsKey(tokenClass))
{
return(PrefixParselets[tokenClass]);
}
return(null);
}
/// <summary>
/// Registers a token type to a new PrefixOperatorParselet
/// </summary>
/// <param name="opToken">Token type to register</param>
public static void RegisterPrefixOperator(TokenType opToken)
{
Logger.Log(LogLevel.Debug, Logger.REGISTRY,
"Registering prefix operator parselet for token " + opToken.ToString());
PrefixParselets.Add(opToken, new PrefixOperatorParselet(Precedence.PREFIX));
}
/// <summary>
/// Registers a token type to a prefix parselet
/// </summary>
/// <param name="token">Token type to register</param>
/// <param name="parselet">Parselet to register to</param>
public static void RegisterPrefix(TokenType token, IPrefixParselet parselet)
{
Logger.Log(LogLevel.Debug, Logger.REGISTRY,
"Registering prefix parselet for token " + token.ToString());
PrefixParselets.Add(token, parselet);
}
