// - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
/// <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;
}
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
/// <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" );
}
IExpression exp = ParseAddExpression();
string leftover = string.Empty;
while ( CurrentToken.type != TokenType.EOF )
{
leftover += CurrentToken.value;
Next();
}
if ( !string.IsNullOrEmpty( leftover ) )
{
throw new TrailingTokensException( "Trailing characters: " + leftover );
}
return exp;
}