private Expression GetExpression(String function)
{
var operatorFound = false;
for (var i = function.Length - 1; i >= 0; i--)
{
operatorFound |= IsOperator(function[i]);
if (ShouldEvaluateMultiplicativeExpression(function, operatorFound, i))
{
var multiplicativeExpressionIndex = i;
while (InMultiplicativeExpression(function, multiplicativeExpressionIndex))
multiplicativeExpressionIndex--;
if (multiplicativeExpressionIndex > 0)
{
var multiplicativeExpression = GetExpression(function.Substring(multiplicativeExpressionIndex + 1));
var nonMultiplicativeFunction = function.Substring(0, multiplicativeExpressionIndex);
var left = GetExpression(nonMultiplicativeFunction);
var right = new Expression() { Value = multiplicativeExpression.Evaluate() };
var nonMultiplicativeOperator = function[multiplicativeExpressionIndex];
var nonMultiplicativeExpression = ExpressionFactory.Get(nonMultiplicativeOperator, left, right);
return nonMultiplicativeExpression;
}
}
if (CanBuildExpression(function, operatorFound, i))
return BuildExpression(function, i);
}
return new Expression() { Value = Convert.ToDouble(function) };
}
private Expression BuildExpression(String function, Int32 i)
{
var number = function.Substring(i + 2);
var left = GetExpression(function.Substring(0, i + 1));
var right = new Expression() { Value = Convert.ToDouble(number) };
return ExpressionFactory.Get(function[i + 1], left, right);
}
public static Expression Get(Char @operator, Expression left, Expression right)
{
switch (@operator)
{
case '/': return new DivisionExpression(left, right);
case '*': return new MultiplicationExpression(left, right);
case '-': return new SubtractionExpression(left, right);
case '+':
default: return new AdditionExpression(left, right);
}
}
public AdditionExpression(Expression left, Expression right)
{
this.left = left;
this.right = right;
}
public MultiplicationExpression(Expression left, Expression right)
{
this.left = left;
this.right = right;
}
public SubtractionExpression(Expression left, Expression right)
{
this.left = left;
this.right = right;
}
public DivisionExpression(Expression left, Expression right)
{
this.left = left;
this.right = right;
}