Re: hash locate_matching_entry()

[John Darrington]

On Wed, Oct 08, 2008 at 10:36:47AM -0400, Jason Stover wrote:
     On Wed, Oct 08, 2008 at 10:25:19AM -0400, Jason Stover wrote:
     > I'm having some trouble getting a matching entry in my
     > hash table. It looks like the problem is here:
     > 
     > /* Locates an entry matching TARGET.  Returns the index for the
     >    entry, if found, or the index of an empty entry that indicates
     >    where TARGET should go, otherwise. */
     > static inline unsigned
     > locate_matching_entry (struct hsh_table *h, const void *target)
     > {
     >   unsigned i = h->hash (target, h->aux);
     > 
     >   assert (h->hash_ordered);
     >   for (;;)
     >     {
     >       void *entry;
     >       i &= h->size - 1;
     >       entry = h->entries[i];
     >       if (entry == NULL || !h->compare (entry, target, h->aux))
     >       return i;
     >       i--;
     >     }
     > }
     > 
     > In my code, h->compare (entry, target, h->aux) returns 1 when
     > entry and target match. So I would think locate_matching_entry()
     > should return i, but it doesn't because of the !h->compare (...).
     > Should this line be:
     > 
     >       if (entry == NULL || h->compare (entry, target, h->aux))
     
     John just clarified over IRC that the return value here is supposed to be
     strcmp-ish: 0 for a match. 

This is why I always encourage people to write 

if ( 0 == strcmp (...)) 

instead of 

if ( !strcmp (...))

J'

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