public ExpressionBase Parse(List<Token> postFix)
{
var stack = new ExpressionStack();
ExpressionBase root = null;
ExpressionBase left = null;
ExpressionBase right = null;
foreach (var token in postFix)
{
switch (token.Type)
{
case TokenType.Function:
root = new FunctionExpression(stack.Pop(), (string)token.Data);
stack.Push(root);
break;
case TokenType.Delimiter:
switch (token.Data.ToString())
{
case "()":
root = new DelimiterExpression(stack.Pop());
stack.Push(root);
break;
case "{}":
root = stack.Pop();
stack.Push(root);
break;
}
break;
case TokenType.Number:
root = new NumericExpression(int.Parse(token.Data.ToString()));
stack.Push(root);
break;
case TokenType.Constant:
root = new ConstantExpression((ConstantType)token.Data);
stack.Push(root);
break;
case TokenType.Variable:
root = new VariableExpression((string)token.Data);
stack.Push(root);
break;
case TokenType.Operator:
switch (token.Data.ToString())
{
case "~":
root = new UnaryMinusExpression(stack.Pop());
stack.Push(root);
break;
case "+":
right = stack.Pop();
left = stack.Pop();
if (left is VariadicOperatorExpression && (left as VariadicOperatorExpression).Type == OperatorType.Add)
{
(left as VariadicOperatorExpression).Add(right);
root = left;
stack.Push(root);
}
else
{
root = new VariadicOperatorExpression(OperatorType.Add, left, right);
stack.Push(root);
}
break;
case "-":
if (this.TreatMinusAsUnaryMinusInVariadicPlus)
{
right = new UnaryMinusExpression(stack.Pop());
left = stack.Pop();
if (left is VariadicOperatorExpression && (left as VariadicOperatorExpression).Type == OperatorType.Add)
{
(left as VariadicOperatorExpression).Add(right);
root = left;
stack.Push(root);
}
else
{
root = new VariadicOperatorExpression(OperatorType.Add, left, right);
stack.Push(root);
}
}
else // treat it at binary operator
{
right = stack.Pop();
left = stack.Pop();
root = new BinaryOperatorExpression(left, right, OperatorType.Subtract);
stack.Push(root);
}
break;
case "*":
right = stack.Pop();
left = stack.Pop();
if (left is VariadicOperatorExpression && (left as VariadicOperatorExpression).Type == OperatorType.Multiply)
{
(left as VariadicOperatorExpression).Add(right);
root = left;
stack.Push(root);
}
else
{
root = new VariadicOperatorExpression(OperatorType.Multiply, left, right);
stack.Push(root);
}
break;
case "/":
right = stack.Pop();
left = stack.Pop();
root = new BinaryOperatorExpression(left, right, OperatorType.Divide);
stack.Push(root);
break;
case "^":
right = stack.Pop();
left = stack.Pop();
root = new BinaryOperatorExpression(left, right, OperatorType.Power);
stack.Push(root);
break;
}
break;
}
}
return root;
}
//1/a^n = a^-n
public static ExpressionBase ReverseVariableWithNegativeExponent(ExpressionBase expression, List<ExpressionBase> selection)
{
//If expression is a fraction. e.g. 1/a^n
BinaryOperatorExpression binaryexpression = expression as BinaryOperatorExpression;
if (binaryexpression != null && binaryexpression.Type == OperatorType.Divide)
{
//If numerator is 1 and denominator is power. e.g. 1 and a^n
NumericExpression numericexpression = binaryexpression.Left as NumericExpression;
BinaryExpression power = binaryexpression.Right as BinaryExpression;
if (numericexpression != null && numericexpression.Value == "1" && power != null && power.Type == OperatorType.Power)
{
//return power with minus exponent. e.g. a^-n
UnaryMinusExpression unaryminus = new UnaryMinusExpression(power.Right.Clone());
BinaryExpression mysuggestion = new BinaryOperatorExpression(power.Left.Clone(), unaryminus.Clone(), OperatorType.Power);
return mysuggestion;
}
}
return null;
}
