I don't want to explain how it works right nowWell, I do. FILL, in the built-in help, is shown as FILL Array, Value [, Offset [, Number of elements]]. 'Offset' is a single number. In a 1D array, it corresponds exactly to the index. In a 2D array, it corresponds to (second index + (second dimension size)*(first index)). For 3D, (third index + (third dimension size)*(second index + (second dimension size)*(first index))). For 4D, the pattern continues. So, the program uses COPY to copy the array in question to a placeholder array. The placeholder array's elements are FILLed with their own 'offset' value. Then, array index [1,0] contains the size of the second dimension, the number of times this fits into the LEN of the array is the size of the first dimension. The code assumes the size of the first dimension is at least 2. It can be adapted for 3D, 4D arrays, but there is no way (so far as I know) to know, given just an array, how many dimensions it has.
