Simplify list.add of unknown amount of entries-CodePudding

So I am currently working on a calculator.

One of the requirements is to store the history, which I currently do in a list.

While I have simplified alot of code I can't get my head around simplifying this

           if (amountNumbers == 2)
            {
                memory.Add(userNumbers[0].ToString()   " "   op   " "   userNumbers[1].ToString()   " = "   calculation.ToString());
                userNumbers.Clear();
            }
            if (amountNumbers == 3)
            {
                memory.Add(userNumbers[0].ToString()   " "   op   " "   userNumbers[1].ToString()   " "   op   " "   userNumbers[2].ToString()   " = "   calculation.ToString());
                userNumbers.Clear();
            }
            if (amountNumbers == 4)
            {
                memory.Add(userNumbers[0].ToString()   " "   op   " "   userNumbers[1].ToString()   " "   op   " "   userNumbers[2].ToString()   " "   op   " "   userNumbers[3].ToString()   " = "   calculation.ToString());
                userNumbers.Clear();
            }
            if (amountNumbers == 5)
            {
                memory.Add(userNumbers[0].ToString()   " "   op   " "   userNumbers[1].ToString()   " "   op   " "   userNumbers[2].ToString()   " "   op   " "   userNumbers[3].ToString()   " "   op   " "   userNumbers[4].ToString()   " = "   calculation.ToString());
                userNumbers.Clear();
            }

Any idea how I simplify this and make the adding dynamic depending on how many values the user has chosen? Preferably I want to store the whole string within one index since that is how the history is being displayed.

CodePudding user response：

Easy, loop over userNumbers and build your string, then add it to memory once you're done. Like so:

// Ensure that we don't get an 'IndexOutOfBoundsException'
// By clamping  'amountNumbers' to the length if 'userNumbers' if it's larger
if (amountNumbers > userNumbers.Length)
    amountNumbers = userNumbers.Length;

// You could use a normal 'string' and '...  = ...' but 'StringBuilder' is more efficient
var sb = new StringBuilder();
for (int i = 0; i < amountNumbers; i  )
    sb.Append($"{userNumbers[i].ToString()} ");

// Add the calculation, no space at the start required as the loop adds a trailing space
sb.Append($"= {calculation.ToString()}");

memory.Add(sb.ToString());

CodePudding user response：

Use .Take() to get some number of users, and String.Join to combine strings with some separator between each:

var users = userNumbers.Take(amountNumbers).Select(s => s.ToString());
var str = string.Join(" "   op   " ", users);
memory.Add(str   " = "   calculation.ToString());

CodePudding user response：

You can just Join userNumbers values with " " op " " separator, then concat calculation at end:

string lastExpression = string.Join(" "   op   " ", userNumbers)   // Join values
                        " = "   calculation.ToString(); // Concat calculation result
memory.Add(lastExpression);
userNumbers.Clear();