Re: Thick vs. Thin bindings

[Marius Amado Alves <amado.alves@netcabo.pt>]

Jeff Houck wrote:
> As I continue to evaluate Ada in the role of a game dev language, I've 
> run across references to "thick" and "thin" bindings and I'm a bit 
> confused.
> My initial design goals are to keep the number of external dependancies 
> to a minimum with most of the support code written in Ada. I would like 
> the code interfaces to be as simple as possible to implement for a 
> designer. I believe this would necessitate a "thick" binding. Is that 
> correct? Would anyone like to elaborate on the pros and cons of these 
> two binding methodologies? Further reading material? Tutorials? Thx!

Thick and thin are ends of a spectrum. Usually a binding is somewhere
inside the range but not exactly at one end. An Ada binding is an Ada 
unit that represents some external system. Usually the Ada unit is a 
package and the external system is a C function library. Here the thin 
extreme of the spectrum would correspond to the most one-to-one mapping 
you could make between the Ada entities and the C entities. My package 
Pgsql [1] provides a nice pedagogical example. It has three software levels:

    1. Ada package Pgsql
    2. Ada package Libpq
    3. C function library "libpq"

Unit 1 depends on 2 depends on 3. The binding 2-3 is the thinest, and 
1-3 is the thickest.

[1] Pgsql is a minimal Postgres binding available at
http://www.liacc.up.pt/~maa/files/Pgsql.zip