[Freeciv-Dev] Re: (PR#6257) recodify map_pos<->index conversion to use native positions

["Jason Short" <jdorje@xxxxxxxxxxxxxxxxxxxxx>]

rwetmore@xxxxxxxxxxxx wrote:
> Bzzzt  ... remember recent history, don't relive it :-).
> 
> Jason Short wrote:
> 
>>Gregory Berkolaiko wrote:
>>
>>
>>>On Tue, 23 Sep 2003, Jason Short wrote:
> 
> [...]
> 
>>>How about introducing 2 new macros
>>>     map_to_native_x
>>>     map_to_native_y
>>
>>Clever.  This is generally the type of thing we want to avoid - since 
>>most of the time it will only lead to misuse - but here it is helpful.
> 
> 
> Actually, very stupid. map_adjust_x() and map_adjust_y() memories should
> hopefully rekindle the endless hassles of assuming that the two coordinates
> are independent. The transformation of a gen-topology 2-D coordinate pair
> cannot assume independence as the first extension case below shows.
> 
> The equivalence operation applies only to the current standard to native
> mappings, and will be very shortlived - so short that hopefully the clever
> stupidity of it will not have time to sink in :-).

It is quite safe to take a function that is (int x int -> int x int) and 
filter the results so that it's (int x int -> int).  It's just that 
there aren't very many reasons why you'd ever want to do this, since one 
coordinate without the other usually won't do you much good.

What map_adjust_[xy] did was limit the input so that the function was 
simply (int -> int) - which is unworkable.

The only acceptable alternative I see is to make this operation a 
(possibly inline) function.

jason