djones@megatest.UUCP (Dave Jones) (01/28/89)
From article <19579@agate.BERKELEY.EDU>, by bowles@eris.berkeley.edu (Jeff A. Bowles): ... > The only thing I really miss is something you Unix-types will recognize > from awk (and perhaps from Algol 68?) - > for (t in table) > process(table[t]); > But that's another story.... > It's easy enough to add, given its utility. I have a number of "container-classes", one of which is called "Hash". You have to use a few more keystrokes than you would in AWK, but it's not _too_ hard on the fingers, if you're a reasonably good typist. Container classes have similar initializers and iterators. Various kinds of objects have associated with them a function which will hash an object, and a function which will determine whether or not two objects are equivalent. (Equivalent objects hash to the same number.) So you're not restricted to using only a few kinds of keys and values, as you are in AWK. A typical kind of object would be a "binding" -- a record which contains a key and a value. I've used automatic variables in the example. I also have canned functions which will get objects from malloc space and initialize them, if that is appropriate.) extern int Some_type_eq_func(); /* boolean */ extern unsigned int Some_type_hash_func(); { Hash table; Hash_init(&table, Some_type_eq_func, Some_type_hash_func); /* Code that puts things into the hash-table, and looks ** them up randomly has been omited... */ { Hash_iter next; Some_type *object; for( Hash_iter_init(&next, &table); object = (char*)Hash_iter_next(&next); object != 0 ) { process(object); } } Hash_clean(&table); } I also have lists, queues, stacks, avl_trees, priority-queues, and so on, all of which have iterators.