Re: Renaming vs assignment to constant

[Shark8 <onewingedshark@gmail.com>]

On Friday, December 6, 2013 4:48:41 PM UTC-7, adambe...@gmail.com wrote:
> 
> > I think the big difference happens when the result has subcomponents:
> >     ch   : constant Character:= 'X';             -- Character X.
> >     temp : String  renames Character'Image(ch);  -- Its image: 'X'.
> >     ch2  : Character renames temp(2);            -- The unquoted character.

Size of Ch:    Assuming 8.
Size of temp:  24 + Bounds(assuming 64).
Size of Ch2:   None, it's a reference-to/alias-of Temp(2).

Total 96 bits.

> What is the big difference between that and
>     ch   : constant Character:= 'X';                -- Character X.
>     temp : constant String := Character'Image(ch);  -- Its image: 'X'.
>     ch2  : constant Character := temp(2);           -- The unquoted character.

Size of Ch:    Assuming 8.
Size of temp:  24 + Bounds(assuming 64).
Size of Ch:    Assuming 8.

Total 104 bits.


Obviously this will really only make a real difference performance-wise when the renamed object's type is large, but there're other reasons to use renames, like component selection of deeply composed objects... but that's a different topic.