Re: [Glsdk-devel] The use of anonymous structures

[H. H. <hen...@gm...>]

On Sun, Aug 24, 2008 at 4:44 AM, Jason McKesson <ko...@gm...> wrote:

>  Henri Häkkinen wrote:
>
>
>
> On Sun, Aug 24, 2008 at 4:19 AM, Jason McKesson <ko...@gm...> wrote:
>
>>  Henri Häkkinen wrote:
>>
>> Does anyone have anything to say on this, please? I am currently working
>> hard on the GLM and I think we should resolve the issue of how we actually
>> define the math types.
>>
>>  Well, the VC++ compiler issue pretty much ends #2 as a possibility. If #1
>> doesn't work for you, that leaves #3.
>>
>
> Well no, this is not true at all. The VC compiler issues is only about
> anonymous structures. For example, this generates a warning:
>
> typedef struct GLMvec2f_s {
>   union {
>     GLfloat v[2];
>     struct {
>       GLfloat x, y;
>     }
>   };
> } GLMvec2f;
>
> While this does not:
>
> typedef struct GLMvec2f_s {
>   union {
>     GLfloat v[2];
>     struct GLMvec2fcoords_s {
>       GLfloat x, y;
>     }
>   };
> } GLMvec2f;
>
>   Admittedly it's been a while since I last used pure C, but if I'm
> reading that right, to access the x or y members, I would need:
>
> GLMvec2f someValue;
>
> someValue.GLMvec3fcoords_s.x = 0.5f
>
> This is a pretty clear violation of design goal #2: Simplicity. And if the
> inner struct can't be accessed with a simple ".x", then what's the point in
> having it at all?
>

No that is not correct at all.

There is a difference between the name of the structure and the name of the
variable. When you write in C like this:

struct FOO {
  int baz;
} fizban;

You access baz inside the struct like this:

fizban.baz = 12;

When we have the vector type:

typedef struct GLMvec2f_s {
  union {
    GLfloat v[2];
    struct GLMvec2fcoords_s {
      GLfloat x, y;
    };
  };
} GLMvec2f;

You access it normally;

GLMvec2f v;
v.x = 10.0f;

The 'GLMvec2fcoords_s' is a structure name, nor a variable name.



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-- 
Henri 'henux' Häkkinen