function for inverse relative path?

[Timothee Cour]

relativePath works with un-normalized paths, and I'd want the same for
inverseRelativePath, eg: should work with:
`/a//b/./c/bar.d` and `c//bar.d` => `/a//b`

unfortunately buildNormalizedPath(rel) will prepend getcwd to `rel` so
it's a tad more complex than just calling buildNormalizedPath on both
arguments; which is way would be nice to have in std.path


On Wed, Dec 6, 2017 at 8:55 PM, Jonathan M Davis via Digitalmars-d
<digitalmars-d at puremagic.com> wrote:
> On Wednesday, December 06, 2017 17:36:04 Timothee Cour via Digitalmars-d
> wrote:
>> what would be a robust way to do this `inverseRelativePath`, and
>> should that be in std.path?
>>
>> ```
>> auto a="/a/b/c.d";
>> auto b="b/c.d";
>> assert(inverseRelativePath(a, b) == "/a");
>> assertThrown(inverseRelativePath(a, "c2.d"));
>> ```
>
> I've never heard of inverse relative paths, but it looks like all you're
> doing is looking for a substring match at the end and returning the parts at
> the front that don't match. If you're doing that, you could simply do
> something like
>
> enforce(lhs.length >= rhs.length, "some error message");
> if(lhs[rhs.length .. $] == rhs)
>     return lhs[0 .. rhs.length];
> throw new Exception("some error message");
>
> though if you want /a instead of /a/ in your example, some extra code would
> have to be added for properly handling trailing slashes, and depending, you
> might want to normalize paths first (though typically, that sort of thing is
> left up to the caller). It might also need to be enforced that the left-hand
> argument is an absolute path.
>
> - Jonathan M Davis
>