constant array without coded number of elements

Avra

Schreiberling

Gender:
Location: Belgrade, Serbia
Age: 53
Homepage: rs.linkedin.com/in…
Posts: 653
Registered: 07 / 2002

Subject:

constant array without coded number of elements

· Posted: 16.06.2014 - 14:06 · #1

I am trying to enter constant array of some type, where I would enter all elements in code. This works fine if I enter the number of array elements (like with MyArr: array[1..3] of TPoint), but I will maintain an array in code that will grow in elements. Sometimes I will have to add 5 elements, sometimes more. Right now I have to increase manually higher array index. I have tried various methods trying to avoid this, but no luck. Is there some way to acomplish this? Something like M5Arr: array[] of TPoint?

Code

type
  TPoint = record
    X, Y, Z: integer;
  end;

const
  APoint: TPoint = (X : 0; Y : 2; Z : 4); // compiles

  MyArr: array[1..3] of TPoint = ((X: 0; Y: 2; Z: 4), // compiles
                                  (X: 5; Y: 1; Z: 0),
                                  (X: 2; Y: 2; Z: 2));

  M1Arr: array[1..SizeOf(longword) div 2] of byte = (2, 3); // compiles

  M2Arr: array[1..High(M2Arr)] of TPoint = ( // internal compiler error
                                  (X: 0; Y: 2; Z: 4),
                                  (X: 5; Y: 1; Z: 0),
                                  (X: 2; Y: 2; Z: 2));

  M3Arr: array[1..Length(M3Arr)] of TPoint = ( // internal compiler error
                                  (X: 0; Y: 2; Z: 4),
                                  (X: 5; Y: 1; Z: 0),
                                  (X: 2; Y: 2; Z: 2));

  M4Arr: array[1..SizeOf(M4Arr) div SizeOf(TPoint)] of TPoint = ( // internal compiler error
                                  (X: 0; Y: 2; Z: 4),
                                  (X: 5; Y: 1; Z: 0),
                                  (X: 2; Y: 2; Z: 2));

  M5Arr: array[] of TPoint = ( // identifier expected error
                                  (X: 0; Y: 2; Z: 4),
                                  (X: 5; Y: 1; Z: 0),
                                  (X: 2; Y: 2; Z: 2));

Administrator

Gender:
Location: Germany
Age: 24
Homepage: e-lab.de
Posts: 5558
Registered: 03 / 2002

Subject:

Re: constant array without coded number of elements

· Posted: 16.06.2014 - 17:07 · #2

Hello Avra,

we don't have variants here. Furthermore we have an one-pass compiler.
So most of your constructions will not work.
Very strange is "length(array)". An array doesn't have any length, only sizeOf.
But SizeOf can only work with an already defined type,var/const.

rolf

Avra

Schreiberling

Gender:
Location: Belgrade, Serbia
Age: 53
Homepage: rs.linkedin.com/in…
Posts: 653
Registered: 07 / 2002

Subject:

Re: constant array without coded number of elements

· Posted: 17.06.2014 - 00:21 · #3

Quote by rh

So most of your constructions will not work.

Well, I will then have to recalculate array length manually after each change. Anyway, hope that something similar to const Arr: array[] of TSomeType =(...) is possible was not big.

Quote by rh

Very strange is "length(array)". An array doesn't have any length, only sizeOf.
But SizeOf can only work with an already defined type,var/const.

While doing a little research about the topic, I have tried few things found. One of them was to see if at compile time I could use Length() of an array demonstrated in runtime use at the end of this article:
http://www.delphibasics.co.uk/Article.asp?Name=Arrays
As you could see from my unfortunate trials, I was pretty desparate... :banghead:

Merlin

Administrator

Gender:
Age: 24
Posts: 1409
Registered: 03 / 2005

Subject:

Re: constant array without coded number of elements

· Posted: 17.06.2014 - 23:24 · #4

Not a lot of help but the compiler can do some calcs for you, so if you have

Code

const
cArrayLen1 : word = 3;

Myarray[0..cArrayLen1] of point = ....

and you want to add 3, you can put

Code

const
cArrayLen1 = 3 + 3;

then to add another 5

Code

const
cArrayLen1 = 3 + 3 + 5;

No very elegant but....

Avra

Schreiberling

Gender:
Location: Belgrade, Serbia
Age: 53
Homepage: rs.linkedin.com/in…
Posts: 653
Registered: 07 / 2002

Subject:

Re: constant array without coded number of elements

· Posted: 20.06.2014 - 01:05 · #5

Thanks for the effort Merlin, but I was hoping that it could be done in a more convenient way. In Arduino I can write this without specifying number of bytes in advance:

Code

byte arr[] = {0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80};

I know that single pass compiler is not convenient for this, but I was hoping that something already exist since we already have

Code

const arr : array[1..8] of byte = 'FileName.ext';

I wouldn't even mind if I could reserve more then entered array elements (which should not be a problem for single pass compiler), but unfortunately this is not valid since compiler asks for all 8 array elements:

Code

arr : array[1..8] of byte = (11, 22, 33); // <<< ERROR

On the other hand, this is not a show stopper so I will learn to live with it.

constant array without coded number of elements

Registered users in this topic