/// <summary>
/// If obj is null or obj is not a Formula, returns false. Otherwise, reports
/// whether or not this Formula and obj are equal.
///
/// Two Formulae are considered equal if they consist of the same tokens in the
/// same order. To determine token equality, all tokens are compared as strings
/// except for numeric tokens, which are compared as doubles, and variable tokens,
/// whose normalized forms are compared as strings.
///
/// For example, if N is a method that converts all the letters in a string to upper case:
///
/// new Formula("x1+y2", N, s => true).Equals(new Formula("X1 + Y2")) is true
/// new Formula("x1+y2").Equals(new Formula("X1+Y2")) is false
/// new Formula("x1+y2").Equals(new Formula("y2+x1")) is false
/// new Formula("2.0 + x7").Equals(new Formula("2.000 + x7")) is true
/// </summary>
public override bool Equals(object obj)
{
// If obj is null, return false.
if (obj == null)
{
return(false);
}
// If obj cannot be cast to Formula, return false.
Formula Formula2 = obj as Formula;
if ((System.Object)Formula2 == null)
{
return(false);
}
// Retrieve each Formula object's tokens.
List <string> Formula1Tokens = this.GetFormulaTokens();
List <string> Formula2Tokens = Formula2.GetFormulaTokens();
// If Formulas contain a non-equal amount of variables, then they are not equal.
if (!(Formula1Tokens.Count == Formula2Tokens.Count))
{
return(false);
}
// Compare the variables from each formula object.
List <string> Formula1Variables = this.GetFormulaVariables();
List <string> Formula2Variables = Formula2.GetFormulaVariables();
// Check that formulas have same number of variables
if (!(Formula1Variables.Count == Formula2Variables.Count))
{
return(false);
}
// Check that all variables are equal.
for (int i = 0; i < Formula1Variables.Count; i++)
{
if (!(Formula1Variables[i] == Formula2Variables[i]))
{
return(false);
}
}
// Variables to contain parsed doubles from tokens for comparison.
double Formula1Double = 0;
double Formula2Double = 0;
for (int i = 0; i < Formula1Tokens.Count; i++)
{
// If current token is a double, attempt to parse the corresponding token from each list.
if (Double.TryParse(Formula1Tokens[i], out Formula1Double))
{
// If the other object's corresponding token is not also a parsable double, return false.
if (!Double.TryParse(Formula2Tokens[i], out Formula2Double))
{
return(false);
}
// If the parsed doubles are not equal, return false.
else if (!(Formula2Double == Formula1Double))
{
return(false);
}
}
// Skip over any variables. (They have already been compared)
if (Formula1Tokens[i].IsValidVariable())
{
continue;
}
// The rest of the tokens should be normalized variables and operators, so we simply compare them.
else if (!(Formula1Tokens[i] == Formula2Tokens[i]))
{
// If tokens are not equal, return false.
return(false);
}
}
// If the for loop completes, the Formula objects are equal by the provided definition.
return(true);
}
