public void ExpressionSerializerSerialize()
{
var parser = new ExpressionSerializer();
ExpressionBase exp;
exp = new BinaryOperatorExpression(
new NumericExpression(1),
new NumericExpression(1),
OperatorType.Add);
Assert.AreEqual("{1}+{1}", parser.Serialize(exp), "{1}+{1}");
exp = new BinaryOperatorExpression(
new NumericExpression(1),
new NumericExpression(1),
OperatorType.Divide);
Assert.AreEqual("{1}/{1}", parser.Serialize(exp), "{1}/{1}");
exp = new BinaryOperatorExpression(
new NumericExpression(1),
new NumericExpression(1),
OperatorType.Multiply);
Assert.AreEqual("{1}*{1}", parser.Serialize(exp), "{1}*{1}");
exp = new BinaryOperatorExpression(
new NumericExpression(1),
new NumericExpression(1),
OperatorType.Power);
Assert.AreEqual("{1}^{1}", parser.Serialize(exp), "{1}^{1}");
exp = new BinaryOperatorExpression(
new NumericExpression(1),
new NumericExpression(1),
OperatorType.Subtract);
Assert.AreEqual("{1}-{1}", parser.Serialize(exp), "{1}-{1}");
}
//a^-n = 1/a^n
public static ExpressionBase VariableWithNegativeExponent(ExpressionBase expression, List<ExpressionBase> selection)
{
//If expression is a power. e.g. a^-n
BinaryOperatorExpression binaryexpression = expression as BinaryOperatorExpression;
if (binaryexpression != null && binaryexpression.Type == OperatorType.Power)
{
//If exponent of power is unary minus. e.g. -n
UnaryMinusExpression unaryexpression = binaryexpression.Right as UnaryMinusExpression;
if (unaryexpression != null && binaryexpression.Left != null && binaryexpression.Right != null)
{
//Return reciprocal of power with unary minus removed in exponent. e.g. 1/a^n
BinaryExpression power = new BinaryOperatorExpression(binaryexpression.Left.Clone(), unaryexpression.Expression.Clone(), OperatorType.Power);
return new BinaryOperatorExpression(new NumericExpression(1), power, OperatorType.Divide);
}
}
return null;
}
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;
}
//a*a*...*a = a^n where n is an integer.
public static ExpressionBase ProductToExponentRule(ExpressionBase expression, List<ExpressionBase> selection)
{
//If expression is a product.
VariadicExpression product = expression as VariadicOperatorExpression;
if (product != null && product.Type == OperatorType.Multiply)
{
//If all operands are equal.
if (product.Where((operand) => product[0] == operand).Count() == product.Count)
{
//Return power.
BinaryExpression suggestion = new BinaryOperatorExpression(product[0].Clone(), new NumericExpression(product.Count), OperatorType.Power);
return suggestion;
}
}
return null;
}
// a*{b/c} = {a*b}/c
public static ExpressionBase ProductOfConstantAndFraction(ExpressionBase expression, List<ExpressionBase> selection)
{
//If expression is a product with to operands
var variadicExpression = expression as VariadicOperatorExpression;
if (variadicExpression != null && variadicExpression.Type == OperatorType.Multiply && variadicExpression.Count == 2)
{
BinaryOperatorExpression fraction = null;
ExpressionBase other = null;
//Find which operand is a fraction
if ((fraction = variadicExpression[0] as BinaryOperatorExpression) != null && fraction.Type == OperatorType.Divide)
{
other = variadicExpression[1];
}
else if ((fraction = variadicExpression[1] as BinaryOperatorExpression) != null && fraction.Type == OperatorType.Divide)
{
other = variadicExpression[0];
}
else
{
//Return null of non of the operands is a fraction
return null;
}
//Multiply numerator with other operand
VariadicOperatorExpression numerators = new VariadicOperatorExpression(OperatorType.Multiply, fraction.Left.Clone(), other.Clone());
//Return fraction
BinaryOperatorExpression suggestion = new BinaryOperatorExpression(numerators.Clone(), fraction.Right.Clone(), OperatorType.Divide);
return suggestion;
}
return null;
}
//a/b = a*b^-1
public static ExpressionBase FractionToProductRule(ExpressionBase expression, List<ExpressionBase> selection)
{
//If expression a fraction. e.g. a/b
BinaryExpression fraction = expression as BinaryExpression;
if (fraction != null && fraction.Type == OperatorType.Divide)
{
//Convert denominator to power of -1. b => b^-1
ExpressionBase exponent = new BinaryOperatorExpression(
fraction.Right.Clone(),
new UnaryMinusExpression(new NumericExpression(1)),
OperatorType.Power
);
//Return product of numerator and power. a*b^-1
ExpressionBase suggestion = new VariadicOperatorExpression(
OperatorType.Multiply,
fraction.Left.Clone(),
exponent
);
return suggestion;
}
else
{
return null;
}
}
//a^c * b^c = (a*b)^c
public static ExpressionBase CommonPowerParenthesisRule(ExpressionBase expression, List<ExpressionBase> selection)
{
//If expression is a product. e.g. a^c * b^c
VariadicOperatorExpression product = expression as VariadicOperatorExpression;
if (product != null && product.Type == OperatorType.Multiply)
{
ExpressionBase commonPower = null;
List<ExpressionBase> baseList = new List<ExpressionBase>();
//Foreach operand in product
foreach (ExpressionBase operand in product)
{
//If operand is a power
BinaryOperatorExpression power = operand as BinaryOperatorExpression;
if (power != null && power.Type == OperatorType.Power)
{
//If power's exponent equals the common exponent
if (power.Right == commonPower || commonPower == null)
{
//Add power's base to list
commonPower = power.Right;
baseList.Add(power.Left);
}
else
{
return null;
}
}
else
{
return null;
}
}
if (baseList.Count > 1)
{
//Initialize product of all bases in the list.
VariadicOperatorExpression resultProduct = new VariadicOperatorExpression(OperatorType.Multiply, baseList[0].Clone(), baseList[1].Clone());
resultProduct.Add(baseList.Skip(2).Select((b) => b.Clone()).ToList());
//return exponent with product as base and common exponent. e.g. (a*b)^c
BinaryOperatorExpression result = new BinaryOperatorExpression(resultProduct, commonPower.Clone(), OperatorType.Power);
return result;
}
}
return null;
}
