Example on how to use klist.h
pfeatherstone opened this issue · comments
Please could you provide an example on how to use klist.h. I'm having to forward declare structures defined by the macro expansion which i'm pretty sure is not the way to do it.
I think line 100 of klist.h should be removed. Even if you have an empty list, the head and tail pointers are non zero. Therefore when you free the list kmp_free gets called.
@larseggert I know you use klib. Do you agree?
I'm not using klist though.
Fair enough. I think way more effort was put into khash.h That is really well documented and works perfectly
Personally I find the usefulness of klist to be minimal at best. First, you almost always would be better with kvec, and second if you really need a linked list, then an intrusive list would be better to avoid the extra allocations.
Incidentally removing line 100 of klist.h works fine. There doesn’t seem to be any memory leaks. Using it is fairly straight forward actually. My bad
Linked list like objects (say... ropes) are very useful but per object lists are rarely a good structure to use.
@trapexit Thanks that's a great video. I love watching Bjarne. Wouldn't you say it's a bit easier to use lists when you want to remove a single element in the middle of the container? With vectors you have to move the remaining elements back into a contiguous space whereas with lists you just have to update the pointer to the "next" or "prev" nodes. So there are no memmove's, just update a single pointer.
You should always try to pick or design a data structure based on your needs. If order isn't important or removes are rare it'd be just as fast to copy the last element over the one removed or to copy n+1 - m to n - m-1. Updating pointers seems faster but you have to account for the total workflow. Pointers are indirection. That indirection is more costly than direct access in an array. Using pointers means data could be scattered around memory and might not cache well. Arrays can be brought into caches more efficiently.
You have to consider how your data structure will be accessed. What's the cost of those behaviors. How often they are done. Etc.
If speed isn't a concern use whatever you're comfortable with but generally speaking linked lists should be considered anti-patterns on modern hardware. Data locality is important and linked lists almost couldn't be worse for that.