for loop question

The question is about looping through the following structure

Code:

struct  hostent { 
        char    *h_name;        /* official name of host */ 
        char    **h_aliases;    /* alias list */ 
        int     h_addrtype;     /* host address type */ 
        int     h_length;       /* length of address */ 
        char    **h_addr_list;  /* list of addresses from name server */ 
#ifndef _POSIX_C_SOURCE 
#define h_addr  h_addr_list[0]  /* address, for backward compatiblity */ 
#endif /* !_POSIX_C_SOURCE */ 
};

ive seen people use

Code:

//with pointers
for( char const*const* alias = hp->h_aliases; 
       *alias != NULL; 
       ++alias

and

Code:

// with indexing 
  for( int i=0; 
       hp->h_aliases[i]; 
       ++i)

When you use a for loop using pointers this case, why is the person explicit about NULL, but with indexing, it's implicit? ie not using

hp->h_aliases[i] != 0

Originally Posted by cdalten

When you use a for loop using pointers this case, why is the person explicit about NULL, but with indexing, it's implicit?

Dunno. Personal preference and/or laziness?

Okay. I thought I was maybe missing something.

Explicitly testing against NULL may be intended to make it clearer to those who may not see the equivalence as clearly.

I always do != NULL because it's a define so I pretend that it has an unknown value even though I'm aware it's 0 which I guess is good because then my code can be compiled in the year 4352 where NULL has been changed to (-243). Besides, all compilers will optimize if (var != 0) to become if (var).