public Expression Build(string expression)
{
var stack = new Stack <Expression>();
foreach (var item in expression.Split(new[] { " " }, StringSplitOptions.RemoveEmptyEntries))
{
var operatorInfo = ArithmeticalOperatorFactory.Create(item);
var context = new ExpressionContext();
if (operatorInfo.Type == OperatorType.Constant)
{
if (!decimal.TryParse(operatorInfo.Value, out var value))
{
throw new InvalidExpressionFormatException($"{operatorInfo.Value} is not a good value for operand.");
}
stack.Push(Expression.Constant(value));
continue;
}
if (operatorInfo.Type == OperatorType.Operator)
{
context.Right = stack.Pop();
context.Left = stack.Pop();
}
var @operator = operatorInfo.CreateExpression(context);
stack.Push(@operator);
}
if (stack.Count != 1)
{
throw new InvalidExpressionFormatException("Something wrong with your expression");
}
return(stack.Pop());
}
public string Transform(string input)
{
if (input.NullOrWhiteSpace())
{
throw new ArgumentNullException("input");
}
var stack = new Stack <OperatorInfo>();
var result = new StringBuilder();
var inputChars = Regex.Replace(input, @"\s+", "");
foreach (var inputChar in inputChars)
{
var item = ArithmeticalOperatorFactory.Create(inputChar.ToString());
if (item.Type == OperatorType.Operator)
{
if (stack.Count > 0)
{
var topOperator = stack.Peek();
while ((item.OperatorAssociationType == OperatorAssociationType.Right && (int)item.Prioity < (int)topOperator.Prioity || item.OperatorAssociationType == OperatorAssociationType.Left && (int)item.Prioity <= (int)topOperator.Prioity) && stack.Count > 0)
{
AppendOperator(result, stack.Pop());
if (stack.Count > 0)
{
topOperator = stack.Peek();
}
}
}
stack.Push(item);
result.Append(Delimeter);
continue;
}
if (item.Value == OpenParenthesis)
{
stack.Push(item);
continue;
}
if (item.Value == CloseParenthesis)
{
var operatorInfo = stack.Pop();
while (operatorInfo.Value != OpenParenthesis && stack.Count != 0)
{
result.Append(Delimeter).Append(operatorInfo.Value);
operatorInfo = stack.Pop();
}
continue;
}
result.Append(inputChar);
}
AppendAllOperatorsFromStack(stack, result);
return(result.ToString().Trim());
}