/// <summary>
/// Creates a Formula from a string that consists of an infix expression written as
/// described in the class comment. If the expression is syntactically incorrect,
/// throws a FormulaFormatException with an explanatory Message.
///
/// The associated normalizer and validator are the second and third parameters,
/// respectively.
///
/// If the formula contains a variable v such that normalize(v) is not a legal variable,
/// throws a FormulaFormatException with an explanatory message.
///
/// If the formula contains a variable v such that isValid(normalize(v)) is false,
/// throws a FormulaFormatException with an explanatory message.
///
/// Suppose that N is a method that converts all the letters in a string to upper case, and
/// that V is a method that returns true only if a string consists of one letter followed
/// by one digit. Then:
///
/// new Formula("x2+y3", N, V) should succeed
/// new Formula("x+y3", N, V) should throw an exception, since V(N("x")) is false
/// new Formula("2x+y3", N, V) should throw an exception, since "2x+y3" is syntactically incorrect.
/// </summary>
public Formula(String formula, Func <string, string> normalize, Func <string, bool> isValid)
{
values = new Stack <double>();
operators = new Stack <string>();
fE = gibberish;
variables = new ArrayList();
if (normalize == null)
{
normalizer = s => s;
validator = isValid;
}
else if (isValid == null)
{
normalizer = normalize;
validator = s => true;
}
else
{
normalizer = normalize;
validator = isValid;
}
FormulaConstructorMethod(formula, normalizer, validator);
}
/// <summary>
/// Integer and Variable tokens use the same instructions, so to avoid redundant code, I included this function.
///
/// </summary>
/// <param name="currVal">Integer or Variable Value</param>
private void VariableDoubleInstructions(double currVal)
{
//Exception case: The stack is empty, and can't be "peeked"
if (operators.Count > 0 && operators.Peek().Equals("*"))
{
operators.Pop();
currVal *= values.Pop();
values.Push(currVal);
}
else if (operators.Count > 0 && operators.Peek().Equals("/"))
{
operators.Pop();
double placeHolder = values.Pop();
currVal = placeHolder / currVal;
if (double.IsInfinity(currVal))
{
fE = new FormulaError("Cannot divide by 0");
}
else
{
values.Push(currVal);
}
}
else
{
values.Push(currVal);
}
}
/// Takes two ints and an operator (+, -, *, or /) and completes the operation
private object Compute(double val1, double val2, string optr)
{
object result = new FormulaError("Error: Incorrect operator");
// Addition
if (optr.Equals("+"))
{
result = val1 + val2;
}
// Subtraction
else if (optr.Equals("-"))
{
result = val1 - val2;
}
// Multiplication
else if (optr.Equals("*"))
{
result = val1 * val2;
}
// Division
else if (optr.Equals("/"))
{
if (val2 == 0)
{
return(new FormulaError("Error: Divided by zero"));
}
result = val1 / val2;
}
return(result);
}
/// <summary>
/// Gets numbers and operator to find result
/// </summary>
/// <param name="num2">Second number of equation</param>
/// <param name="num1">First number of equation</param>
/// <param name="oper">Operator to be applied to nums</param>
/// <exception cref="System.ArgumentException">Thrown when trying to divide by zero</exception>
/// <returns>Value found from the equation</returns>
private static double Solve(double num2, double num1, char oper, ref object error)
{
switch (oper)
{
case '+':
return(num1 + num2);
case '-':
return(num1 - num2);
case '*':
return(num1 * num2);
case '/':
if (num2 == 0)
{
error = new FormulaError("Attempted to divide by zero.");
return(0);
}
else
{
return(num1 / num2);
}
}
return(0);
}
/// <summary>
/// String of an operator does algebra on the numbers given, returns value after algebra
/// </summary>
/// <param name="given"></param>
private object OperatorAlgebra(string operation, double num1, double num2)
{
double sum = 0;
if (operation == "+")
{
sum = num1 + num2;
op.Pop();
}
else if (operation == "-")
{
sum = num1 - num2;
op.Pop();
}
else if (operation == "*")
{
sum = num1 * num2;
op.Pop();
}
else if (operation == "/")
{
if (num2 == 0.0)
{
FormulaError formulaError = new FormulaError("Divisable by zero error");
return(formulaError);
}
sum = num1 / num2;
op.Pop();
}
return(sum);
}
/// <summary>
/// Creates a Formula from a string that consists of an infix expression written as
/// described in the class comment. If the expression is syntactically invalid,
/// throws a FormulaFormatException with an explanatory Message.
///
/// The associated normalizer is the identity function, and the associated validator
/// maps every string to true.
/// </summary>
public Formula(String formula) :
this(formula, s => s, s => true)
{
values = new Stack <double>();
operators = new Stack <string>();
fE = gibberish;
variables = new ArrayList();
normalizer = s => s;
validator = s => true;
FormulaConstructorMethod(formula, normalizer, validator);
}
/// <summary>
/// Evaluates this Formula, using the lookup delegate to determine the values of
/// variables. When a variable symbol v needs to be determined, it should be looked up
/// via lookup(normalize(v)). (Here, normalize is the normalizer that was passed to
/// the constructor.)
///
/// For example, if L("x") is 2, L("X") is 4, and N is a method that converts all the letters
/// in a string to upper case:
///
/// new Formula("x+7", N, s => true).Evaluate(L) is 11
/// new Formula("x+7").Evaluate(L) is 9
///
/// Given a variable symbol as its parameter, lookup returns the variable's value
/// (if it has one) or throws an ArgumentException (otherwise).
///
/// If no undefined variables or divisions by zero are encountered when evaluating
/// this Formula, the value is returned. Otherwise, a FormulaError is returned.
/// The Reason property of the FormulaError should have a meaningful explanation.
///
/// This method should never throw an exception.
/// </summary>
public object Evaluate(Func <string, double> lookup)
{
Stack <string> operatorStack = new Stack <string>();
Stack <double> valueStack = new Stack <double>();
//Using a try catch to catch a divide by 0 error, or an argument exception error from the lookup
//If these exceptions are caught, it will return a formula error.
//If not, it will return a double.
try
{
foreach (string s in ValidTokens)
{
if (IsLeftParen(s))
{
operatorStack.Push(s);
}
else if (IsRightParen(s))
{
if (IsPlusOrMinusOnStack(operatorStack))
{
double computedValue = PerformPlusMinusComputation(operatorStack, valueStack);
valueStack.Push(computedValue);
}
operatorStack.Pop();
if (IsMultiplyOrDivideOnStack(operatorStack))
{
double computedValue = PerformMultiplyDivideComputation(operatorStack, valueStack, 0, false);
valueStack.Push(computedValue);
}
}
else if (IsMultiplyOrDivide(s))
{
operatorStack.Push(s);
}
else if (IsPlusOrMinus(s))
{
if (IsPlusOrMinusOnStack(operatorStack))
{
double computedValue = PerformPlusMinusComputation(operatorStack, valueStack);
valueStack.Push(computedValue);
}
operatorStack.Push(s);
}
else if (IsNum(s))
{
double value = double.Parse(s);
HandleIntOrVariable(operatorStack, valueStack, value);
}
else if (IsVariable(s))
{
double value = lookup(s);
HandleIntOrVariable(operatorStack, valueStack, value);
}
}
//End of for loop
if (operatorStack.IsEmpty())
{
return(valueStack.Pop());
}
else
{
return(PerformPlusMinusComputation(operatorStack, valueStack));
}
}
catch (ArgumentException)
{
FormulaError error = new FormulaError("Invalid variable");
return(error);
}
catch (DivideByZeroException)
{
FormulaError error = new FormulaError("Division by 0");
return(error);
}
}
public void PublicGradingTestDivideByZero()
{
Formula x = new Formula("5/0");
FormulaError error_message = new FormulaError("Can not divide by zero.");
Assert.AreEqual(error_message, x.Evaluate(s => 0.0));
}
/// <summary>
/// Evaluates this Formula, using the lookup delegate to determine the values of
/// variables. When a variable symbol v needs to be determined, it should be looked up
/// via lookup(normalize(v)). (Here, normalize is the normalizer that was passed to
/// the constructor.)
///
/// For example, if L("x") is 2, L("X") is 4, and N is a method that converts all the letters
/// in a string to upper case:
///
/// new Formula("x+7", N, s => true).Evaluate(L) is 11
/// new Formula("x+7").Evaluate(L) is 9
///
/// Given a variable symbol as its parameter, lookup returns the variable's value
/// (if it has one) or throws an ArgumentException (otherwise).
///
/// If no undefined variables or divisions by zero are encountered when evaluating
/// this Formula, the value is returned. Otherwise, a FormulaError is returned.
/// The Reason property of the FormulaError should have a meaningful explanation.
///
/// This method should never throw an exception.
/// </summary>
public object Evaluate(Func <string, double> lookup)
{
//These stacks are used to hold the operators and operands of the infix expression
Stack <double> values = new Stack <double>();
Stack <String> operators = new Stack <String>();
FormulaError divideByZero = new FormulaError("Error: Divide by 0. Check expression for any possible " +
"divsions by 0.");
//Traverses through the string
foreach (String token in GetTokens(normalizedExp))
{
//If the token is an integer
if (Double.TryParse(token, out double parsedDouble))
{
if (!HandleDouble(parsedDouble, operators, values))
{
return(divideByZero);
}
}
//If the token is a variable (checks to see if the first character is a letter)
else if (token.StartsAsVar())
{
//Try to lookup the variable and pass it to the same function that handles a normal integer
//If an exception is thrown by the delegate looking up the variable, return an error
try
{
parsedDouble = lookup(token);
if (!HandleDouble(parsedDouble, operators, values))
{
return(divideByZero);
}
}
catch (Exception)
{
return(new FormulaError("A value for the variable " + token + "could not be found. " +
"Check the variable or the lookup delegate"));
}
}
//If the token is + or -
else if (token.Equals("+") || token.Equals("-"))
{
HandlePlusMinus(operators, values);
//Pushes the token (+ or -) onto the stack always
operators.Push(token);
}
//If the token is * or / or (
else if (token.Equals("*") || token.Equals("/") || token.Equals("("))
{
operators.Push(token);
}
//If the token is )
else if (token.Equals(")"))
{
if (operators.IsOnTop <String>("+") || operators.IsOnTop <String>("-"))
{
HandlePlusMinus(operators, values);
}
//At this point, only a "(" should be on top of the stack.
operators.Pop();
//If there is a value on the stack, pop it and hand it over to the int handling function
if (values.Count > 0)
{
if (!HandleDouble(values.Pop(), operators, values))
{
return(divideByZero);
}
}
}
}
//Operator and value stack checking after the last token has been processed.
//If there are no operators, there should be 1 value on the stack - the result.
//If there is an operator, there should be only 1 and it should be a + or -.
//If this is the case, there should be two values on the value stack to be processed.
if (operators.Count == 0 && values.Count == 1)
{
return(values.Pop());
}
//Operators count should be 1 and values count should be 2
else
{
HandlePlusMinus(operators, values);
return(values.Pop());
}
}
/// <inheritdoc />
/// <summary>
/// Constructs an EvaluationException with the given FormulaError.
/// </summary>
/// <param name="error">The error to store in this exception.</param>
public EvaluationException(FormulaError error)
{
Error = error;
}
/// <summary>
/// Evaluates this Formula, using the lookup delegate to determine the values of
/// variables. When a variable symbol v needs to be determined, it should be looked up
/// via lookup(normalize(v)). (Here, normalize is the normalizer that was passed to
/// the constructor.)
///
/// For example, if L("x") is 2, L("X") is 4, and N is a method that converts all the letters
/// in a string to upper case:
///
/// new Formula("x+7", N, s => true).Evaluate(L) is 11
/// new Formula("x+7").Evaluate(L) is 9
///
/// Given a variable symbol as its parameter, lookup returns the variable's value
/// (if it has one) or throws an ArgumentException (otherwise).
///
/// If no undefined variables or divisions by zero are encountered when evaluating
/// this Formula, the value is returned. Otherwise, a FormulaError is returned.
/// The Reason property of the FormulaError should have a meaningful explanation.
///
/// This method should never throw an exception.
/// </summary>
public object Evaluate(Func <string, double> lookup)
{
// vinc: check if formula causes FormulaFormatException
if (!ValidFormat)
{
return(formaterror);
}
/// vinc: check if it is Circular Dependency
if (CircularDependency)
{
FormulaError error = new FormulaError("Circular Dependency");
error.CircularDependency = true;
return(error);
}
//Set up stacks and start distributing the tokens into them
Stack <double> values = new Stack <double>();
Stack <string> operators = new Stack <string>();
//Loop over the tokens
foreach (string token in normalizedFormula)
{
//Integer/Variable handling:
double number;
bool isDouble = false;
if (IsVariable(token))
{
try
{
number = lookup(token);
}
catch (ArgumentException)
{
return(new FormulaError("Variable " + token + " Does Not Exist"));
}
isDouble = true;
}
else
{
isDouble = double.TryParse(token, out number);
}
//Double Handling
if (isDouble)
{
if (IsOnTop(operators, "*") || IsOnTop(operators, "/"))
{
try
{
values.Push(Arithmator(operators.Pop(), values.Pop(), number));
}
catch (DivideByZeroException)
{
return(new FormulaError("Divide by Zero"));
}
}
else
{
values.Push(number);
}
}
//+ or - Operator Handling
if (token.Equals("+") || token.Equals("-"))
{
if (IsOnTop(operators, "+") || IsOnTop(operators, "-"))
{
double b = values.Pop();
double a = values.Pop();
values.Push(Arithmator(operators.Pop(), a, b));
}
operators.Push(token);
}
//* or / operator handling
if (token.Equals("*") || token.Equals("/"))
{
operators.Push(token);
}
//Parenthisis handling
if (token.Equals("("))
{
operators.Push(token);
}
if (token.Equals(")"))
{
if (IsOnTop(operators, "+") || IsOnTop(operators, "-"))
{
double b = values.Pop();
double a = values.Pop();
values.Push(Arithmator(operators.Pop(), a, b));
operators.Pop(); //Pop the openparen from the operators stack
}
if (IsOnTop(operators, "*") || IsOnTop(operators, "/"))
{
try
{
double b = values.Pop();
double a = values.Pop();
values.Push(Arithmator(operators.Pop(), a, b));
}
catch (DivideByZeroException)
{
return(new FormulaError("Error: Divide by Zero"));
}
}
}
}
//End behavior
if (operators.Count == 0)
{
return(values.Pop());
}
else
{
double b = values.Pop();
double a = values.Pop();
values.Push(Arithmator(operators.Pop(), a, b));
return(values.Pop());
}
}
