// - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
/// <summary>
/// Parse a string representation of a parametric function into an
/// expression tree that can be later evaluated.
/// </summary>
/// <param name="function">The function to parse</param>
/// <returns>An expression tree representing the function parsed</returns>
public static IExpression Parse(string function)
{
_tokenizer = new Tokenizer(function);
_currentToken = new Token("", TokenType.None);
if (!Next())
{
throw new InvalidExpressionException("Cannot parse an empty function");
}
var exp = ParseAddExpression();
var leftover = string.Empty;
while (_currentToken.Type != TokenType.Eof)
{
leftover += _currentToken.Value;
Next();
}
if (!string.IsNullOrEmpty(leftover))
{
throw new TrailingTokensException("Trailing characters: " + leftover);
}
return exp;
}
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
/// <summary>
/// Assign the next token in the queue to CurrentToken
/// </summary>
/// <returns>
/// true if there are still more tokens in the queue,
/// false if we have looked at all available tokens already
/// </returns>
private static bool Next()
{
if (_currentToken.Type == TokenType.Eof)
{
throw new OutOfTokensException("Parsed past the end of the function");
}
_currentToken = _tokenizer.Next();
return _currentToken.Type != TokenType.Eof;
}