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

["Rafa³ Bursig" <bursig@xxxxxxxxx>]

Dnia 2003.09.23 19:46, Jason Short napisa³(a):
> 
> Index positions are ordered based off of native ones.  So the current
> conversion operations (e.g., map_pos_to_index and index_to_map_pos)
> are
> no good when we start using native positions.
> 
> Unfortunately going through native coordinates requires an
> intermediate
> pair of variables, which is a problem with macros.  There are three
> possible solutions:
> 
> 
> 1.  Change them both into standard functions.
> 
> This is the prettiest solution.  The only drawback is that it's 
> slower - about a 5-10% slowdown in autogame performance in a few 
> tests I did.
> 
> 
> 2.  Change them both into inline functions.
> 
> This is almost as pretty, and just as fast as the current code (for
> reasonable compilers).  The only real drawback is that we're not
> "supposed" to use inline functions in freeciv.  Also compilers that
> don't recognize inline will give warnings in files that don't use the
> functions (unavoidable when using inline).
> 
> 
> 3.  Keep them as macros with temporary (global) variables in the
> header
> file.
> 
> The obvious drawback is that this is incredibly ugly.  The less
> obvious
> drawback is that the line
> 
>    array[map_pos_to_index(x, y)] = array[map_pos_to_index(x1, y1)]
> 
> is not legal C (just like a ^= b ^= a ^= b).  So without some other
> cleverness either all lines like this will have to be changed (see
> settlers.c and mapgen.c) or this is not an option.  Gcc 3.2.1 just
> gives
> a warning, and *hopefully* compiles it into the proper code:
> 
>    settlers.c:167: warning: operation on `_fc_nat_y' may be undefined
>    settlers.c:167: warning: operation on `_fc_nat_x' may be undefined
>    settlers.c:169: warning: operation on `_fc_nat_y' may be undefined
>    settlers.c:169: warning: operation on `_fc_nat_x' may be undefined
> 
> If only C had tuples...
> 

Jason could you show real map_to_native_pos(...) function/macro.
How complicatet it will be ?

Rafal