How to make a matrix AxB using CRPL?

[pawel345]

I know it's possible but how to do it? I know how to make a List, but how to change a list to a matrix? For example I would like to have a matrix Map Width by Map Height. The concept somehow eludes me. If someone could write a function to handle something like that I would be very thankful.

[Grayzzur]

Basically you just have a bigger list and do the math yourself. That's all an array is behind the scenes.

If you want an array that's 10x10, you make a list of 100, and access element (x+y*10).

Edit: In case it's not clear which 10 to multiply Y by --
Array [Width, Height] would be List [Width*Height] and access element [x,y] in the array would be [x+y*Width] in the list.

[eduran]

I've been using this function:

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CreateListStartingSize(MapWidth mul(MapHeight)) ->2DArray
Set/GetListElement(<-2DArray @Coord2Index(<-x <-y))

:Coord2Index
# takes cell coordinates x and y and transforms them into the corresponding array index
# allows usage of lists (=1D arrays) as if they were two dimensional
# x1 y1 - i1
swap MapHeight mul add

[pawel345]

thanks :D I knew it must have been something easy that I just couldn't get :D

[Clean0nion]

Other than almost all the topics in Builder's Corner, there so far have been no topics of which to me the concept has made no sense - this is the first.

[knucracker]

Here is a 2x2 array.
0 1 2
3 4 5
6 7 8

Note the index of each position.  That is the same as this single dimensional list:
0 1 2 3 4 5 6 7 8

You can represent any n dimensional array with a single dimensional list, so long as you define the extents of each dimension beyond the first dimension ( you must define the the width for instance in a 2 dimensional array).

[Michionlion]

Here's how I think of it, C0.  You basically have a 2D array, right?  However, instead of using colums like this:

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1,1 | 2,1 | 3,1
1,2 | 2,2 | 3,2
1,3 | 2,3 | 3,3


We only designate one index for each coord (that way it fits in a single list), and it loops around, like this:

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0 | 1 | 2
3 | 4 | 5
6 | 7 | 8


Therefore, we can access each 'coordinate' from x,y coordinates by adding 3 for each y increment - for instance, if you wanted to get index 5, which corresponds to 2,1, you take the x coord and then add the y coord multiplied by the width of the array (3), like so:

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x + (y*width)
2 + (1*3)


Note that the array MUST be zero based for this method to work. (if not zero-based, you must add the base amount (so if you started indexing at 1, you would add 1) to the output of the above formula - so it would become base+x+(y*width).  You cannot do this - at least, not easily - with a non-zero based coordinate system without first converting to zeroed. I hope that explains it!

EDIT:  and I spent all that time making this just to have V respond before me.... :P

[Clean0nion]

Right - thanks. I'd just use two lists, but I'm not sure if that would achieve the same effect.

EDIT: That is thanks to both of you, of course.

[Michionlion]

It would achieve the same effect, but with more complication than necessary, although it would be easier to understand.

[Grauniad]

Right - thanks. I'd just use two lists, but I'm not sure if that would achieve the same effect.

EDIT: That is thanks to both of you, of course.

How would you use two lists to represent a 64 x 64 array?

[Clean0nion]

It would achieve the same effect, but with more complication than necessary, although it would be easier to understand.

Which reminds me - and I'll stop posting after this post - one of my projects has about 16 lists in it, 12 of which are used simultaneously, and all are per script per unit. Though in some units only one of the lists is used.

@Grauniad

64 0 do
  64 0 do
    <-x J AppendToList
    <-y I AppendToList
  loop
loop

something like that

[Michionlion]

Right - thanks. I'd just use two lists, but I'm not sure if that would achieve the same effect.

EDIT: That is thanks to both of you, of course.

How would you use two lists to represent a 64 x 64 array?

hmm... you're right!  You'd have to do a list inside a list, and I don't know if that is possible.

[Clean0nion]

Right - thanks. I'd just use two lists, but I'm not sure if that would achieve the same effect.

EDIT: That is thanks to both of you, of course.

How would you use two lists to represent a 64 x 64 array?

hmm... you're right!  You'd have to do a list inside a list, and I don't know if that is possible.

Yes I lied that I wouldn't post anymore, but you should understand that I have no idea what I'm taking about.

Actually, you could do a list inside a list now that I think about it...
using <-! and ->!

[eduran]

hmm... you're right!  You'd have to do a list inside a list, and I don't know if that is possible.

You can do lists inside lists, but to store a 64x64 matrix you'd need 9 size-8 lists in total.

[Karsten75]

I have no idea what I'm taking about.

word.

hmm... you're right!  You'd have to do a list inside a list, and I don't know if that is possible.

You can do lists inside lists, but to store a 64x64 matrix you'd need 9 size-8 lists in total.

I'dthink, in my simplicity, that you'd have to have more than that...