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Problem converting c to cpp with matrices

 
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Ghoti



Joined: 31 Dec 2005
Posts: 288
PostPosted: Tue Dec 12, 2006 6:22 am    Post subject: Problem converting c to cpp with matrices Reply with quote
Hi folks,

Hi folks,

i use the matrix functions that were part of the examples in the SDK:
Code:
void matrix_multiply(float* result, float* a, float* b)
   {
      unsigned int i,j,k;
      float temp[16];

      for (i = 0; i < 4; ++i)
      {
         for (j = 0; j < 4; ++j)
         {
            float t = 0.0f;
            for (k = 0; k < 4; ++k)
               t += a[(k << 2)+j] * b[(i << 2)+k];
            temp[(i << 2)+j] = t;
         }
      }

      memcpy(result,temp,sizeof(float)*16);
   }


when i use this in a C source file i use it like this:

Code:
matrix_identity((float*)&world);


      
         matrix_identity((float*)&tmpworld);
         
         matrix_multiply((float*)&world, &world, &tmpworld);

this works fine.

since its part of a 3d game i want it to be in cpp cause of the object oriented way of programming.
well i copied the code but i got an error with that exact code:
Code:
bj.cpp:165: error: cannot convert 'ScePspFMatrix4*' to 'float*' for argument '2' to 'void matrix_multiply(float*, float*, float*)'
O
so i tried in doing (float*) infront of the &world, and &tmpworld. This stopped the error but my code is not running anymore.

my question: Why this difference in code? why does my old code won't work anymore?
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My PSP games:

Boxy II: http://www.ghoti.nl/boxyii.php
Elementals: http://www.ghoti.nl/Elementals.php
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rapso



Joined: 28 Mar 2005
Posts: 147
PostPosted: Tue Dec 12, 2006 9:04 am    Post subject: Reply with quote
how du u declare world and tmpworld? probably this are already pointers?
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cooleyes



Joined: 18 May 2006
Posts: 125
PostPosted: Tue Dec 12, 2006 5:54 pm    Post subject: Re: Problem converting c to cpp with matrices Reply with quote
Ghoti wrote:
Hi folks,

Hi folks,

i use the matrix functions that were part of the examples in the SDK:
Code:
void matrix_multiply(float* result, float* a, float* b)
   {
      unsigned int i,j,k;
      float temp[16];

      for (i = 0; i < 4; ++i)
      {
         for (j = 0; j < 4; ++j)
         {
            float t = 0.0f;
            for (k = 0; k < 4; ++k)
               t += a[(k << 2)+j] * b[(i << 2)+k];
            temp[(i << 2)+j] = t;
         }
      }

      memcpy(result,temp,sizeof(float)*16);
   }


when i use this in a C source file i use it like this:

Code:
matrix_identity((float*)&world);


      
         matrix_identity((float*)&tmpworld);
         
         matrix_multiply((float*)&world, &world, &tmpworld);

this works fine.

since its part of a 3d game i want it to be in cpp cause of the object oriented way of programming.
well i copied the code but i got an error with that exact code:
Code:
bj.cpp:165: error: cannot convert 'ScePspFMatrix4*' to 'float*' for argument '2' to 'void matrix_multiply(float*, float*, float*)'
O
so i tried in doing (float*) infront of the &world, and &tmpworld. This stopped the error but my code is not running anymore.

my question: Why this difference in code? why does my old code won't work anymore?


you must use force typecast
just like
Code:

matrix_identity((float*)&tmpworld);
matrix_multiply((float*)&world, (float*)&world, (float*)&tmpworld);
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Ghoti



Joined: 31 Dec 2005
Posts: 288
PostPosted: Tue Dec 12, 2006 6:59 pm    Post subject: Reply with quote
@rapso: I declare it in both situations this way:

Code:
         ScePspFMatrix4   world;
         ScePspFMatrix4   tmpworld;


the only difference is that i this in cpp for in a class header and in the C source i do it just at the top of the source file

@cooleyes: yes i have done that, but why that difference, why do i have to do that in cpp and not in c?
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Boxy II: http://www.ghoti.nl/boxyii.php
Elementals: http://www.ghoti.nl/Elementals.php
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chp



Joined: 23 Jun 2004
Posts: 313
PostPosted: Tue Dec 12, 2006 7:09 pm    Post subject: Reply with quote
Because C++ is not as relaxed when it comes to type checking as ordinary C is, and thats a good thing.

If you intend to always access ScePspFMatrix4-objects using that method, rewrite it to take a pointer of that type, or write a inlined overload that does the conversion for you.
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Ghoti



Joined: 31 Dec 2005
Posts: 288
PostPosted: Tue Dec 12, 2006 7:26 pm    Post subject: Reply with quote
ah okay thanks :)
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My PSP games:

Boxy II: http://www.ghoti.nl/boxyii.php
Elementals: http://www.ghoti.nl/Elementals.php
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