예제 #1
0
        public ExpressionizeResult GenerateExpression()
        {
            ExpressionizeResult result = CreateExpression(MinOperatorPrecedence);

            if (currentToken != null && currentToken.Type == TokenType.ParenRight)
            {
                return(ExpressionizeResult.NewError(ErrorInfo.UnexpectRightParen));
            }

            return(result);
        }
예제 #2
0
        ExpressionizeResult CreateExpression(int basePrecedence)
        {
            Expression single = null;

            // Make an atom.
            ExpressionizeResult atomResult = CreateAtom();

            if (!atomResult.Success)
            {
                return(atomResult);
            }

            // Atomizing succeeded.
            single = atomResult.CalculatedExpression;

            while (true)
            {
                // After an atom might be an operator, an argument or another expression.

                // End of the token list.
                if (currentToken == null)
                {
                    break;
                }

                // Operator after an atom.
                if (TokenType.Operator.HasFlag(currentToken.Type))
                {
                    BinaryType binaryType = currentToken.Type.ToBinaryType();

                    int opPrecedence = binaryType.GetPrecedence();

                    if (opPrecedence < basePrecedence)
                    {
                        break;
                    }

                    int nextPrecedence = binaryType.IsLeftAssociative() ? (opPrecedence + 1) : opPrecedence;

                    GetNextToken();
                    ExpressionizeResult rightResult = CreateExpression(nextPrecedence);

                    if (!rightResult.Success)
                    {
                        return(rightResult);
                    }

                    Expression left  = single;
                    Expression right = rightResult.CalculatedExpression;

                    single = new BinaryExpression(left, right, binaryType);
                }
                else
                {
                    // Variable or left parenthesis after an atom,
                    // connect them with implied multiplication.
                    if (currentToken.Type == TokenType.Variable || currentToken.Type == TokenType.ParenLeft)
                    {
                        BinaryType binaryType = BinaryType.ImpliedMultiply;

                        int opPrecedence = binaryType.GetPrecedence();

                        if (opPrecedence < basePrecedence)
                        {
                            break;
                        }

                        int nextPrecedence = binaryType.IsLeftAssociative() ? (opPrecedence + 1) : opPrecedence;

                        // No need to consume the operator token.

                        ExpressionizeResult rightResult = CreateExpression(nextPrecedence);

                        if (!rightResult.Success)
                        {
                            return(rightResult);
                        }

                        Expression right = rightResult.CalculatedExpression;

                        single = new BinaryExpression(single, right, binaryType);
                    }
                    else
                    {
                        if (currentToken.Type == TokenType.Constant)
                        {
                            return(ExpressionizeResult.NewError(ErrorInfo.ExpectOperator));
                        }

                        // The current expression ends if we encounter anything else.
                        break;
                    }
                }
            }

            return(ExpressionizeResult.NewSuccess(single));
        }
예제 #3
0
        ExpressionizeResult CreateAtom()
        {
            if (currentToken == null)
            {
                return(ExpressionizeResult.NewError(ErrorInfo.ExpectExpression));
            }

            if (currentToken.Type == TokenType.Constant)
            {
                Constant constant = (Constant)currentToken;
                GetNextToken();

                // Create a new constant expression.
                ConstantExpression constantExpression = new ConstantExpression(constant.Value);
                return(ExpressionizeResult.NewSuccess(constantExpression));
            }
            else if (currentToken.Type == TokenType.Variable)
            {
                Variable variable = (Variable)currentToken;
                GetNextToken();

                // Create a new argument expression.
                VariableExpression argumentExpression = new VariableExpression(variable.Name);
                return(ExpressionizeResult.NewSuccess(argumentExpression));
            }
            else if (TokenType.UnaryOperator.HasFlag(currentToken.Type))
            {
                UnaryType unaryType = currentToken.Type.ToUnaryType();

                GetNextToken();
                // Since unary operator is left associative, we add 1 to the base precedence.
                ExpressionizeResult childResult = CreateExpression(unaryType.GetPrecedence() + 1);

                if (!childResult.Success)
                {
                    return(childResult);
                }

                Expression childExpression = childResult.CalculatedExpression;

                // Create a new unary expression.
                UnaryExpression unaryExpression = new UnaryExpression(childExpression, unaryType);
                return(ExpressionizeResult.NewSuccess(unaryExpression));
            }
            else if (currentToken.Type == TokenType.ParenLeft)
            {
                GetNextToken();
                // Try to make a sub-expression enclosed by this left parenthesis.
                ExpressionizeResult subResult = CreateExpression(MinOperatorPrecedence);

                if (!subResult.Success)
                {
                    return(subResult);
                }

                Expression subExpression = subResult.CalculatedExpression;

                // Expect a matching right parenthesis.
                if (currentToken != null && currentToken.Type == TokenType.ParenRight)
                {
                    GetNextToken();
                    return(ExpressionizeResult.NewSuccess(subExpression));
                }
                else
                {
                    return(ExpressionizeResult.NewError(ErrorInfo.ExpectRightParen));
                }
            }
            else if (currentToken.Type == TokenType.Function)
            {
                // A function has two parts:
                // - An identifier(name)
                // - Its arguments enclosed in a pair of parens.

                FunctionHeader    functionHeader = (FunctionHeader)currentToken;
                List <Expression> argumentsList  = new List <Expression>();

                GetNextToken();

                if (currentToken != null && currentToken.Type == TokenType.ParenLeft)
                {
                    GetNextToken();

                    // Only create expressions for each argument if the function requires any.
                    if (functionHeader.ArgumentCount > 0)
                    {
                        // NOTE: Handle multiple args here.
                        ExpressionizeResult argumentResult = CreateExpression(MinOperatorPrecedence);

                        if (!argumentResult.Success)
                        {
                            return(argumentResult);
                        }

                        argumentsList.Add(argumentResult.CalculatedExpression);
                    }

                    if (currentToken != null && currentToken.Type == TokenType.ParenRight)
                    {
                        GetNextToken();

                        // Create a function expression.
                        FunctionExpression functionExpression =
                            new FunctionExpression(
                                functionHeader.Name,
                                functionHeader.Target,
                                argumentsList);

                        return(ExpressionizeResult.NewSuccess(functionExpression));
                    }
                    else
                    {
                        return(ExpressionizeResult.NewError(ErrorInfo.ExpectRightParen));
                    }
                }
                else
                {
                    return(ExpressionizeResult.NewError(ErrorInfo.ExpectLeftParen));
                }
            }

            return(ExpressionizeResult.NewError(ErrorInfo.ExpectExpression));
        }