> On Oct 22, 2017, at 16:05, Neil Van Dyke <n...@neilvandyke.org> wrote:
> I could be missing something, but I think a filename completion procedure
> (not the DrRacket integration part) might be a doable exercise for a budding
> Racket programmer, so long as they already have a basic familiarity with
> using the filesystem and shell as a normal user.
(forgive me for hijacking this thread.)
I see what you’re saying. I was thinking of all of the fancy features that tcsh
has around filename completion, but it’s true that most of those aren’t things
I use every day. You definitely would want “~” to work right, though, and I had
imagined a stateful notion of “current directory”, but really, that’s probably
just gilding the lily.
> Point them to the "Paths" and "Filesystem" sections of the Racket Reference,
> and tell them they just need a few procedures from each (probably including
> `split-path` and `directory-list`).
> They might want to first make a procedure like this:
> (path-completions path-or-string?)
> ==> (listof completion-string)
> And then make a second procedure, which uses the first procedure, then adds
> an additional step, to let it return two values instead of one:
> (path-completion-prefix-and-suffixes path-or-string?)
> ==> (values prefix-string-shared-by-all-completions
> (listof completion-remainder-after-any-shared-prefix-string))
> Then, when a user is interactively doing completion (like when they hit the
> Tab key in a shell), the first value returned by that second procedure is
> what would get added automatically to the path. The second value is the list
> of possible completions following that shared prefix.
> There are a few special cases to consider, but most should be easy to
> recognize and work through, just by thinking methodically about each point in
> your code. For example, what do you do when the input path is relative, or
> when when there are no completions, or when the path is invalid or
> nonexistent or permissions-inaccessible, or when your path is already
> complete. One case that's not obvious from the code: if the path is already
> complete and is a directory, a shell usually completes a directory separator,
> so consider whether you want to do that.
> To make unit tests for these, they'll have to also look at more of the
> "Filesystem" section of the Racket Reference, to create and remove files and
> (I think wrapping a shell process, robustly, is much more difficult.)
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