Re: [PATCH 1/8] xdl_change_compact(): rename some local variables for clarity

On Sat, Aug 13, 2016 at 09:38:33PM +0200, Michael Haggerty wrote:

On 08/04/2016 09:06 AM, Jeff King wrote:

quoted

On Thu, Aug 04, 2016 at 12:00:29AM +0200, Michael Haggerty wrote:

quoted

* ix -> i
* ixo -> io
* ixs -> start
* grpsiz -> groupsize

After your change, I immediately understand three of them. But what is
"io"?

The (pre-existing) convention in this function is that variable names
dealing with the "other" file have a trailing "o"; e.g., (xdf, xdfo),
(rchg, rchgo). There used to also be (i, io), the indexes tracking the
current line number in the file and the other file. But I renamed "i".

Yeah, after reading the rest of the patches, the "o" prefix sort of
started to make sense.

At first I was just going to add a comment for variable "io", but in
trying to figure out its exact semantics I realized that this code is
still pretty hard to follow. Part of the problem is that "the line in
the other file corresponding to a line in the to-be-compacted file" is
not a well-defined concept. In fact it is *groups of lines* that
correlate with each other. So I totally refactored the function, using a

    struct group {
            long start, end;
    };

as a kind of a cursor used to iterate through the groups on both sides.
I think the result is a lot easier to read, and while refactoring I
found and fixed another bug in the pre-existing code :-O

That sounds like it would be nicer. And bug fixes are always good.

Don't kill yourself polishing up the function names, though (unless you
keep finding bugs. ;) ).

-Peff