How to create a macro on a condition inside a if statement

Question

I need to iterate a for loop nested inside of a while loop for several different conditions.

The only change in the code for each statement is the comparison condition to apply.

Turns out I am copy-pasting all of the code multiple times and changing the direction of the greater-less than symbol.

for example:

if (direction.horizontal == UIScrollDirectionLeft) {
    int column = startColumn+1;
    while (column < maxAllowed) {
        for (int row = minRow; row < maxRow; row++) {
            repeated code
        }
        column++;
 } else {
    int column = minColumn -1;
    while (column >= 0) {
        for (int row = minRow; row < maxRow; row++) {
            repeated code
        }
        column--;
    }
}

Is it possible to do a macro for the condition operator in order to facilitate code reuse?

I would really like something which could look like this:

int  startColumn = (direction.horizontal == UIScrollDirectionLeft) ? (startColumn+1) : minColumn -1;
SignOfOperator theSignInTheWhile = (direction.horizontal == UIScrollDirectionLeft) ? "<" : ">=";
int conditionToTestInWhile = (direction.horizontal == UIScrollDirectionLeft) ? maxAllowed : 0;

while(startColumn,theSignInTheWhile,conditionToTestInWhile) {
  // repeated code
}

I have another 4 cases like the one above...

Answer 1

You only need the loop code once. Just change the step value and terminating value. For example:

int start_column, end_column, column_step;
   :
switch (direction.horizontal) {
  case UIScrollDirectionLeft:
    column = start_column + 1;
    column_step = 1;
    end_column = max_allowed;
    break;
  case UIScrollDirectionRight:
    column = min_column - 1;
    column_step = -1;
    end_column = -1;
    break;
  :
}
while (column != end_column) {
  for (int row = minRow; row < maxRow; row++) {
    repeated_code();
  }
  column += column_step;
}