/// <summary>
/// Returns true if two Equations are the same. e.g. x+y=2 and 2x+2y=4
/// </summary>
/// <param name="other"></param>
/// <returns></returns>
public bool IsEquivalent(Equation other)
{
Solve(Variable.NULL);
other.Solve(Variable.NULL);
if (IsEmpty(_rightPart) && IsEmpty(other.RightPart))
return true;
if (_rightPart.Count != other.RightPart.Count)
return false;
_rightPart = _rightPart.OrderBy(x => x.Variable.Name).ToList();
var coef1 = _rightPart[0].Coefficient;
var coef2 = other.RightPart[0].Coefficient;
var a = coef1/coef2;
for (int i = 0; i < _rightPart.Count; i++)
{
var var1Name = _rightPart[i].Variable.Name;
bool hasSameVariable = false;
foreach (var expression in other.RightPart)
{
if (expression.Variable.Name == var1Name)
{
hasSameVariable = true;
coef2 = expression.Coefficient;
break;
}
}
if (!hasSameVariable)
return false;
coef1 = _rightPart[i].Coefficient;
if ((Math.Abs(coef1 / coef2 - a) > TOLERANCE))
return false;
}
if (_leftPart.Count == 0 && other.LeftPart.Count == 0)
return true;
coef1 = _leftPart[0].Coefficient;
coef2 = other._leftPart[0].Coefficient;
if ((Math.Abs(coef1/coef2 - a) < TOLERANCE))
return true;
return false;
}
private void SubstituteVariablesValues()
{
foreach (var variable in _variablesList)
{
if (variable.Value.All(x => x.Variable.Equals(Variable.NULL)))
continue;
var equation = new Equation(new Expression(1, variable), variable.Value);
variable.Value = new List<Expression>();
equation.Solve(variable);
variable.SetValue(equation.RightPart);
}
}
public static Equation operator *(Equation eq1, double value)
{
var leftPart = new List<Expression>();
var rightPart = new List<Expression>();
eq1.LeftPart.ForEach(x =>
{
var expression = new Expression(x.Coefficient*value, x.Variable);
leftPart.Add(expression);
});
eq1.RightPart.ForEach(x =>
{
var expression = new Expression(x.Coefficient*value, x.Variable);
rightPart.Add(expression);
});
var newEquation = new Equation(leftPart, rightPart);
return newEquation;
}
