[Freeciv-Dev] Re: unit flags/capabilities

[Andrew Sutton <ansutton@xxxxxxx>]

On Thursday 29 November 2001 04:04 am, Raimar Falke wrote:
> On Wed, Nov 28, 2001 at 03:59:47PM -0500, Andrew Sutton wrote:
 > it'd take a considerable amount of patching to work the changes back to
> > the server and client, but IMHO i think it's not a bad idea.
> >
> > thoughts?
>
> Why? The server core only uses enum unit_flag_id. And this is good
> IMHO. The server AI needs extra infos about how to use certain unit
> types: enum unit_role_id was added.
>
> So what are your problems with this? Running out of flags? We can fix
> this in a transparent way (no changes of the format of the rulesets,
> no changes of the code, just the network code, unit_flag and ruleset
> reading). It may necessary to have other infos about the units (for
> example if you program an AI). But I don't see that you are doing
> this.

1. it's a clumsy implementation.
2. it isn't very extensible
3. it groups widely different types of data together into one bitfield.
4. it separates out data that should be there.
5. adding a new implementation won't change the old code or the rulesets

this is a more graceful way to introduce capabilities to units than to 
continually define and insert enumerations and bitfields into a structure. 
there's been alot of talk about coding style? that's bad.

the point is that all of that information describes some capability of the 
unit AND follows the same base subscription pattern (can have multiple 
properties). therefore, it deserves to be in one place - type definition.

if you wanted to gracefully add new informatics for a new type of unit, then 
sticking that data into the unit structure is bad style too. now, you end up 
with a single structure that contains all the information for all units and 
its overkill. it's clumsy. it's harder to maintain. it's harder to extend.

if you really want to add a new unit that defines a new field, say fuel (for 
aircraft), then the correct thing to do would be to "derive" a new structure 
for it. you'd end up with this:

struct unit
{
        unit_type       type;
        unit_flags      flags;
        // other generic information
};

struct aircraft
{
        struct unit     base;
        unsigned        fuel;
};

voila! graceful extension of the unit type (or something similar). this is, 
by the way, the RIGHT way to code that.

the whole point is that people have been kludging this game together for a 
long time. i'm starting to go thru field by field and undo some of those 
problems. i'm sure some parts of the game are actually gracefully and 
artfully written, but not unit code.

andy