Use of constants as array bounds?

[darknatter]

What is wrong with the following? Surely it must be possible to use a constant to specify array specs

const
        NUM_CONTROL_TYPES: Integer = 8;

var
   ControlsByType: Array[0..NUM_CONTROL_TYPES] of Array of TControl;


Err: Can't evaluate constant expression

[Thausand]

That write able constant (typed constant). That no true constant. Write able constant can have change value runtime. https://www.freepascal.org/docs-html/ref/refse10.html

edit: may be have look here https://www.freepascal.org/docs-html/ref/refsu14.html and have choose static array or dynamic array.

[jamie]

What is wrong with the following? Surely it must be possible to use a constant to specify array specs

const
        NUM_CONTROL_TYPES: Integer = 8;

var
   ControlsByType: Array[0..NUM_CONTROL_TYPES] of Array of TControl;


Err: Can't evaluate constant expression

Code: Pascal  [Select][+][-]

1. Const NUM_CONTROL_TYPES = 8;
2.  

Problem with that is you can't change the value at runtime because its a compile time value which you have for your array as a static fixed size defind at compile time.

 If you a flexible runtime array, then use a Dynamic Array that can be adjusted at runtime.

Jamie

[n7800]

@darknatter, in other words, constants don't require a data type:

Code: Pascal  [Select][+][-]

1. const
2.   NUM_CONTROL_TYPES = 8;          // "true" const
3.   NUM_CONTROL_TYPES: Integer = 8; // not "true" const
4.  

As far as I remember, this was a tweak from old Turbo Pascal for compatibility reasons. When specifying a type, it's like a variable, and a global one at that. You can read more in the links above.