RE: [Dev-C++] ANSI C++ forbids implicit conversion from `void *' in argument passing

[Ioannis V. <no...@ya...>]

> -----Original Message-----
> From: dev...@li... 
> [mailto:dev...@li...] On Behalf 
> Of Ioannis Vranos
> Sent: Monday, February 11, 2002 12:57 AM
> To: Dev-C++
> Subject: RE: [Dev-C++] ANSI C++ forbids implicit conversion 
> from `void *' in argument passing
> 
> 
> In C++ a void * can not be assigned directly in any pointer 
> type without casting, e.g. the result of malloc() needs 
> casting in C++. void * is used a lot in C to emulate generic 
> programming with poor abilities in the particular area, that 
> is to write functions that do things on various types of 
> variables using ancient non type safe techniques. C++ has 
> built in support for generic programming with the best 
> possible way, templates. Templates arre both time efficient, 
> space efficient if you use specializations where is needed 
> and type-safe at the same time. E.g. consider the following 
> C++ C-style code:
> 
> void *add(void *p1, void *p2, const char *type)
> {
>  if(strcmp(type, "int")
> {
>   if(int *resul=(char *)malloc(sizeof(int)))
>  {
>    *result=(int *)p1+(int *)p2;
>     return result;
>  }
> 
>  else if(strcmp(type, "float") 
>  // Pain goes on...
> 
> }
> 
> 
> Consider the template alternative:
> 
> template <class T>
> inline T add(T a, T b)
> {
>  return a+b;
> }
> 
> 
> It is both type safe and maximally efficient.
> 
> 
> So better use templates in the place where you use void * for 
> generic programming.

Tonight i have drunk a bit wine hic, but i just realised that the
original question was about some API. Anyway i made mistakes! in the
previous email in the C-style implementation so here is the correct one:

void *add(void *p1, void *p2, const char *type)
{
  if(!strcmp(type, "int"))
 {
   if(int *result=(int *)malloc(sizeof(int)))
  {
    *result=*(int *)p1+*(int *)p2;
     return result;
  }
 }

 else if(!strcmp(type, "float") 
 // Pain goes on...

}



And the template alternative is better written:

template <class T>
inline T add(const T &a, const T &b)
{
 return a+b;
}


Now if i made more mistakes, sorry fellows it is the wine. :)


Ioannis
 
* Ioannis Vranos
* Programming pages: http://www.noicys.d2g.com
* Alternative URL: http://run.to/noicys