Junio C Hamano wrote:
> Derrick Stolee <stolee@xxxxxxxxx> writes:
>
> > On 12/15/2020 12:53 PM, Elijah Newren via GitGitGadget wrote:
> >> From: Elijah Newren <newren@xxxxxxxxx>
> >>
> >> In a subsequent commit, we will implement the traditional recursiveness
> >> that gave merge-recursive its name, namely merging non-unique
> >> merge-bases to come up with a single virtual merge base. Copy a few
> >> helper functions from merge-recursive.c that we will use in the
> >> implementation.
> >
> > I'm sure these are copies, but...
> >
> >> +static struct commit_list *reverse_commit_list(struct commit_list *list)
> >> +{
> >> + struct commit_list *next = NULL, *current, *backup;
> >> + for (current = list; current; current = backup) {
> >> + backup = current->next;
> >> + current->next = next;
> >> + next = current;
> >> + }
> >
> > The naming of 'next' seems backwards to me, since it is really
> > the "previous" node. Using something like 'previous' makes it
> > clear that you are reversing when you say
> >
> > current->next = previous;
>
> Hmph. I took "next" commit_list as "list is the original one, and
> next is the reversed list, the next generation of what we received".
>
> Calling it "previous" feels even more backwards when you view among
> three "struct commit_list *" pointers, one (the one that holds the
> eventual return value) is primarily used to denote the resulting
> list itself, and the other two are used to point individual elements
> on the original list.
Both feel awkward to me because to me previous/next are actually current
in my mind, and we should return current, not previous/next. Plus
there's no need for current, we can use list, as your example.
This is what I came up with:
struct commit_list *current = NULL;
while (list) {
struct commit_list *tmp = list->next;
list->next = current;
current = list;
list = tmp;
}
return current;
For completeness I checked how Linux does it, and surprisingly
llist_reverse_order() is very close to what I came up with:
struct commit_list *new_list = NULL;
while (list) {
struct commit_list *tmp = list;
list = list->next;
tmp->next = new_list;
new_list = tmp;
}
return new_list;
(obviously translated)
Maybe it's just me, but I find my version easier to read.
Cheers.
--
Felipe Contreras
