while undocumented (?), there seems to be a lot of code
in GHCi regarding commandline completion. but in a
default build, i don't get any benefit from that, as editline
doesn't seem available for mingw (?).
is there a way to get this working on windows? i'm growing
rather tired of typing VeryLongCamelCaseLanguageExtensions
in GHCi sessions, and this would help!-)
if there really is no working editline for windows, is there a
way of pluggin in Malcolm's System.Console.SimpleLineEditor (currently in package readline),
extended to handle completion?
the completion code itself is in haskell, anyway, just that there's
no editline/readline to call this code on windows, right?
Yes, exactly. I believe at one stage there was a readline C library available for mingw, and we
could build the Haskell readline library, but IIRC it was a bit flaky and only worked in some of
the console environments (cmd, MSYS, cygwin, xterm).
I noticed various references to rlwrap (readline wrapper) recently,
so I decided to give it a try. There's a cygwin package for it:
rlwrap runs the specified command, intercepting user input in order
to supply
readline's line editing, persistent history and completion. rlwrap tries
to be as
transparent as possible, keeping track of command's terminal settings, so
that it
can do the right thing when command asks for single keypresses or for a
password.
And it works like a charm!-) Not as specific as the GHCi-builtin
support for completion, but better than just inheriting the command
history scrolling and commandline editing from bash. Some helpful
options:
-c, --complete-filenames
-H, --history-filename file
-r, --remember
Put all words seen on in- and output on the completion list.
So, with
$ rlwrap -c -H /cygdrive/c/Documents\ and\ Settings/cr3/Application\ Data/ghc/rlwrap.log -r
ghcii.sh
I get filename completion, I get completion for language options
that have been suggested in error messages (!-), and I don't have
to spell things out twice, as the session history gets stored (btw,
should there be ghc-version-specific Application\ Data/ghc/ dirs?).
And all the general readline goodies, like incremental history search.
There is probably some more fine-tuning possible, perhaps someone
finds a way to give the rlwrap's readline on-the-fly access to the
session-specific GHCi completion info designed for linked readline?
Even if not, we could probably prep completion in 'rlwrap ghcii.sh'
with the flag reference, and poor Windows users can get the
comforts that non-Windows users are used to with GHCi!-)
Anyway, I thought I'd share this early, before doing more
experimentation.
Enjoy,
Claus
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