[fpc-pascal] Array clearing

[Jürgen Hestermann]

Am 2017-04-04 um 16:54 schrieb Ryan Joseph:
 >> var arr : array of array of Integer;
 >> begin
 >> SetLength(arr, 10, 10);
 > “then the first array stores a pointer to each sub array.”
 > Could you illustrate this is code?
 > I don’t think I’m understanding this exactly like it’s represented in memory.
 > There’s only one “sub array” in this 2x2 array so how does that look in memory?

Why 2x2?
SetLength(arr,10,10) creates a 10x10 array.

I am trying to show the memory allocation for the 10x10 array as a "graphic":

arr --> arr[0],arr[1],arr[2],arr[3],arr[4],arr[5],arr[6],arr[7],arr[8],arr[9]
           |      |      |      |      |      |      |      | |      |
           V      V      V      V      V      V      V      V V      V
         arr[0,0],       .      .      .      .      .      . .    arr[9,0],
         arr[0,1],       .      .      .      .      .      . .    arr[9,1],
         arr[0,2],       .      .      .      .      .      . .    arr[9,2],
arr[0,3], arr[9,3],
arr[0,4], arr[9,4],
arr[0,5], arr[9,5],
...                                                            ...

arr is a single pointer (that points to arr[0]).
arr[0] to arr[9] are (10) pointers located in a continuous memory block each pointing to
arr[0,0],
arr[1,0],
arr[3,0], and so on...
arr[0,0] is a single integer.
arr[0,0] to arr[0,9] are (10) integers located in a continuous memory block.
The same applies for
arr[1,0] to arr[1,9],
arr[2,0] to arr[2,9],
arr[3,0] to arr[3,9], and so on.