Re: OpenGL in Ada

[BrianG <briang000@gmail.com>]

Shark8 wrote:
> On Jul 11, 2:46 pm, a...@att.net wrote:
>> In <i1bktn$uc...@speranza.aioe.org>, tmo...@acm.org writes:
>>>>>>>  Procedure Color    ( red, green, blue : in double );
>>>>>>>  Procedure Color    ( red, green, blue : in float );
>>>> One problem you'll have is if a user wants to make a call with all
>>>> literals, i.e. Color(1, 2, 3) or Color(1.0, 2.0, 3.0), the compiler
>>>> won't know which version to use.  The best solution I've found (besides
>>>> making users specify a type)
>>> And what's wrong with requiring the user to be unambiguous by specifying
>>> a type?  It's unlikely there will be a lot of calls with all literals
>>> (unless generated by some program) so it shouldn't be onerous.  And
>>> "Float'(1.0)" is clearer to the person reading the code five years
>> >from now than "Color_F".
>>
>> What your are forgetting is the openGL is a specification from the openGL
>> group ( opengl.org ), it is just like the Ada RM in that respect.  For a
>> program or package, to be classified as openGL it must comply with "openGL
>> group" openGL specification.  Changing any API part nullify the use of
>> openGL in any part of your system.

I'm sorry, I wasn't aware we had a member of the OpenGL police present. 
  Where do I go to pay my fine?  BTW, it appears the proper name is 
OpenGL, not openGL :-).  Not that I'm picky.

Maybe you ('Anon') ought to actually read the spec you mentioned.  The 
following is a direct quote from that document:
"The declarations shown in this document apply to ANSI C. Languages such 
as C++ and Ada that allow passing of argument type information admit 
simpler declarations and fewer entry points."
(with reference to the GLxxxTypeInterface naming convention.)
[http://www.opengl.org/registry/doc/glspec40.core.20100311.pdf]

>>
>> So, adding or altering any definitions about the given API must comply with
>> the openGL specification. Names of the API functions and procedures with
>> the API defined types are set by this openGL group.
> 
> That seems, on its face, to contradict BrianG's claim:
> 
>> What you have is a way to do it, but that's not what the OP posted.  He had
>> all procedures named Color, so the user doesn't need to worry about
>> implementation.  (If I use Color for Double and want to change my program to
>> use Float, I have to change the names of all calls, even if I use calls where
>> the compiler could determine what I want - and not just calls to Color, many
>> routines would have the same issue.)  This is also what the OpenGL
>> documentation implies should be done in a language like Ada.
> 
> But, if he's correct in this earlier post:
>> (I've tried starting a similar effort, but never got very far.  I was using
>> the OpenGL "red book" as a basis; I find it interesting that the OpenGL
>> definition recognizes that "some languages like Ada and C++" could implement
>> names this way, but every Ada library I've seen follows the C naming scheme.)
> 
> Then my renaming (to get rid of the gl- prefix and parameter-type-
> postfix) and
> overloading them all is a valid OpenGL API.
> 
Not only is it valid, it looks like it's what was expected.  I've never 
seen an implementation that does that.

>> visitwww.opengl.org
>> for more information on openGL and the "openGL group"
>>
>> Also, you may find the API specifications predefined with examples in C that
>> you can alter to Ada there as well.
> 
What I've been using is the online v1.1 "Redbook" 
[http://www.glprogramming.com/red/] - since ObjectAda (from Barnes' 
book) uses that version (last I looked, GNAT/GTKAda didn't provide 
OpenGL on windows).

I've never tried figuring out OpenGL versions - right now the "current 
edition of the Redbook" is version 2.1, but the same page points to 
          a "Specification Version 4.0".  Whatever.