[m-rev.] for post-commit review: change hunks

[Julien Fischer]

On Fri, 28 Jun 2019, Zoltan Somogyi wrote:

> For post-commit review by Julien.

> Compute change hunks from diff sequences.

...

> diff --git a/library/edit_seq.m b/library/edit_seq.m
> index dd606f689..1593889b2 100644
> --- a/library/edit_seq.m
> +++ b/library/edit_seq.m

...

> @@ -351,6 +432,156 @@ flush_deletes_inserts(!Deletes, !Inserts, !Diffs) :-
>      !:Deletes = cord.init,
>      !:Inserts = cord.init.
> 
> +%---------------------------------------------------------------------------%
> +%---------------------------------------------------------------------------%
> +
> +find_change_hunks(ContextSize0, Diffs, CHunks) :-
> +    % If our caller passes us an invalid ContextSize0, we replace it
> +    % with the default context size 3.
> +    % XXX Would programmers prefer us to throw an exception here?

I think so; whichever approach is chosen should be documented.

> +    ( if ContextSize0 > 0 then
> +        ContextSize = ContextSize0
> +    else
> +        ContextSize = 3
> +    ),
> +    find_change_hunks_loop(ContextSize, Diffs, 1, 1, [], RevCHunks),
> +    list.reverse(RevCHunks, CHunks).
> +

...

> +
> +:- pred scan_change_hunk_diffs(int::in, list(diff(T))::in, list(diff(T))::out,
> +    list(diff(T))::in, list(diff(T))::out,
> +    int::in, int::out, int::in, int::out,
> +    int::in, int::out, int::in, int::out) is det.
> +
> +scan_change_hunk_diffs(ContextSize, Diffs, LeftOverDiffs, !RevCHunkDiffs,
> +        !NumDeleted, !NumInserted, !NumUnchanged, !NumContigUnchanged) :-
> +    (
> +        Diffs = [],
> +        LeftOverDiffs = []
> +    ;
> +        Diffs = [HeadDiff | TailDiffs],
> +        (
> +            HeadDiff = unchanged(_),
> +            ( if ContextSize =< !.NumContigUnchanged then
> +                ( if
> +                    scan_joined_context(ContextSize, Diffs, AfterContextDiffs,
> +                        !RevCHunkDiffs, !NumUnchanged)
> +                then
> +                    !:NumContigUnchanged = 0,
> +                    scan_change_hunk_diffs(ContextSize, AfterContextDiffs,
> +                        LeftOverDiffs,
> +                        !RevCHunkDiffs, !NumDeleted, !NumInserted,
> +                        !NumUnchanged, !NumContigUnchanged)
> +                else
> +                    LeftOverDiffs = Diffs
> +                )
> +            else
> +                !:RevCHunkDiffs = [HeadDiff | !.RevCHunkDiffs],
> +                !:NumUnchanged = !.NumUnchanged + 1,
> +                !:NumContigUnchanged = !.NumContigUnchanged + 1,
> +                scan_change_hunk_diffs(ContextSize, TailDiffs, LeftOverDiffs,
> +                    !RevCHunkDiffs, !NumDeleted, !NumInserted,
> +                    !NumUnchanged, !NumContigUnchanged)
> +            )
> +        ;
> +            HeadDiff = deleted(_),
> +            !:RevCHunkDiffs = [HeadDiff | !.RevCHunkDiffs],
> +            !:NumDeleted = !.NumDeleted + 1,
> +            !:NumContigUnchanged = 0,
> +            scan_change_hunk_diffs(ContextSize, TailDiffs, LeftOverDiffs,
> +                !RevCHunkDiffs, !NumDeleted, !NumInserted,
> +                !NumUnchanged, !NumContigUnchanged)
> +        ;
> +            HeadDiff = inserted(_),
> +            !:RevCHunkDiffs = [HeadDiff | !.RevCHunkDiffs],
> +            !:NumInserted = !.NumInserted + 1,
> +            !:NumContigUnchanged = 0,
> +            scan_change_hunk_diffs(ContextSize, TailDiffs, LeftOverDiffs,
> +                !RevCHunkDiffs, !NumDeleted, !NumInserted,
> +                !NumUnchanged, !NumContigUnchanged)
> +        )
> +    ).
> +
> +    % If

That comment is perhaps a touch too concise.

> +:- pred scan_joined_context(int::in, list(diff(T))::in, list(diff(T))::out,
> +    list(diff(T))::in, list(diff(T))::out, int::in, int::out) is semidet.

The diff is fine otherwise.

Julien.