Dear all,
in an array, what would be the code to delete rows that have value equals to zero?
It depends on what your purpose is…
For example if you want a smaller array with non-zero values only, you can transfer an array into another array by looping until max rank of starting array and selecting only the non-zero values to be transferred into destination array, but you would lose the initial ranks, so the purpose is important to start with in order to decide whether losing ranks is compatible with the rest of your code.
Another possibility is: if you want to keep same array and same ranks and what you’re after is the smallest non-zero value, then there would be several different coding possibilities, still depending on final purpose.
But if what you’re after is deleting all intermediate zero values in ranks lower than the max rank, while keeping existing ranks of non-zero values where they are, meaning switching back some zeros to “undefined”, regardless of why, this 3rd possibility couldn’t be done.
One technique I have used is, if the values stored in the array are all going to be positive and/or zero, then multiplying the non required value(s) by -1 makes it/them negative. This allow using a condition that skips the negative values when looping through the array. Depending on application, the CONTINUE and BREAK commands can be useful with the IF statement.. The array stays the same size and the original values are all still intact, though some may be set negative, but multiply by -1 again on a value revert the back to original representation. Index order still maintained with array. Multiplying the whole array inverts the valid elements, to give the invalid values if needed.
When you state, ‘delete rows’, I assume that you mean removing the un-wanted element values and then only being left with the minimum number of elements in the array, or in one continuous block of elements.
Unfortunately, there is no instruction that deletes a single array element, only way to delete an element is to use UNSET($arr), which un-set’s the whole array.
To achieve the goal, you would have to copy all required elements to a temporarily array, only incrementing the new index for required values. The temp array would then hold the wanted values in the smallest array size.
However, you would have to UNSET the original array and re-create it again and copy the temp array to the new array with original name. This is so that any reference to the original array name referenced in the code logic would still work. There is no re-naming of arrays. Then the temp could be UNSET, for next time. LASTSET points to the highest index which is a valid element value.
One thing to note is that, LASTSET($arr) all-way points to the highest valid defined array index, if I remember correctly.
If you just shifted the next required elements value into the un- required values element, continue shifting till all the valid values were in one block, the excess end element(s) will still hold there original values from before the shifting. These excess elements could be set to UNDEFINED or some control value, but the elements would still exist, the last pointed to element index by LASTSET($arr) would be the last valid defined array index of the array, which would not be a valid element value. You could use a separate variable to track the end of the required array elements end position.
Further to the shifting scenario, you could start at the end of the array and shift the element up. The excess elements would fall at the beginning of the array and the external variable could track the start point of valid values. This would mean LASTSET would both point to the last array element which would be valid, so LASTSET could still be easily used. Just the start point would move.
