It sounds like this should be added to the GHCi documentation, even if it's not strictly about GHCi.
David FeuerWell-Typed, LLP -------- Original message --------From: Evan Laforge <qdun...@gmail.com> Date: 12/5/17 4:49 PM (GMT-05:00) To: Brandon Allbery <allber...@gmail.com> Cc: ghc-devs@haskell.org Subject: Re: Long standing annoying issue in ghci Here's what I use: :set prompt "\ESC[46m\STX%s>\ESC[39;49m\STX " I believe \STX is a signal to haskeline for control sequences. Documentation is here: https://github.com/judah/haskeline/wiki/ControlSequencesInPrompt On Tue, Dec 5, 2017 at 12:57 PM, Brandon Allbery <allber...@gmail.com> wrote: > On Tue, Dec 5, 2017 at 12:36 PM, cheater00 cheater00 <cheate...@gmail.com> > wrote: >> >> without color coding the prompt so I can't really turn it off. It >> seems like a simple arithmetic issue somewhere in the readline >> implementation. > > > It's not arithmetic except in the sense that it's not doing *any* math. > Color codes in a terminal are necessarily implemented as character sequences > (this is pretty much the definition of a terminal interface), and haskeline > makes no effort to recognize them, so it treats them the same as displayed > character sequences and skips over them as if they were displayed > characters. > > GNU readline handles this by recognizing the character mode sequences as not > taking up character positions (this is more complex than you think given > that GNU readline doesn't assume all terminals obey the ANSI standard; as it > turns out, neither does haskeline, so it actually gets a bit nasty), and > recognizing the special behavior of carriage return, and providing \[ \] > escapes to declare the sequence inside as "invisible" to to character > positioning (and it's on the person crafting the prompt to insure that it > actually is). Beyond that, it'd actually have to implement a 'terminal > emulator' internally to get it right in all cases --- and i'd be on the user > to ensure their declared terminal type matches the actual one well enough > for the 'terminal emulator' to reflect the terminal's actual behavior, so > it'd be a potential source of even weirder behavior. > > So, (a) haskeline issue, not strictly ghc/ghci, and (b) not really fixable, > but partially work-around-able for common cases. > > -- > brandon s allbery kf8nh sine nomine associates > allber...@gmail.com ballb...@sinenomine.net > unix, openafs, kerberos, infrastructure, xmonad http://sinenomine.net > > _______________________________________________ > ghc-devs mailing list > ghc-devs@haskell.org > http://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-devs > _______________________________________________ ghc-devs mailing list ghc-devs@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-devs
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