Comments on: Colors in GHCi

By: Joel

Joel — Sat, 10 Sep 2011 21:37:08 +0000

Why not go all out and style the output as well? Here’s what I came up:

#!/bin/sh

# Colors
red=`echo “33[91m"`
green=`echo "33[92m"`
yellow=`echo "33[93m"`
blue=`echo "33[94m"`
purple=`echo "33[95m"`
cyan=`echo "33[96m"`

# Bold colors
bold=`echo "33[1m"`
bold_red=`echo "33[1;91m"`
bold_green=`echo "33[1;92m"`
bold_yellow=`echo "33[1;93m"`
bold_blue=`echo "33[1;94m"`
bold_purple=`echo "33[1;95m"`
bold_cyan=`echo "33[1;96m"`

# Color reset
reset=`echo "33[0m"`

# Patterns
double_colon="s/::/$red&$reset/;"
rocket="s/=>/$red&$reset/;"
left_arrow="s//$red&$reset/;"
strings="s/"[^"]*”/$yellow&$reset/g;”
chars=”s/’[a-zA-Z]*’/$purple&$reset/g;”

exec “`which ghc`” –interactive ${1+”$@”} |
sed “$double_colon
$rocket
$right_arrow
$left_arrow
$strings
$chars”

You could really take this pretty far and style all sorts of things. Numbers however can get a bit dicey since the color codes contain numbers.

Though this feels a bit hackish, it works well enough for me.

By: Yifan Yu

Yifan Yu — Tue, 28 Sep 2010 02:53:05 +0000

This works fine. But when I try to edit a file in ghci (`:set editor vim’ was performed) by using:

:e Somefile.hs

Vim gives a warning: Output is not to a terminal, and the file could not be edited.

Is there a way to handle this?

By: enoksrd

enoksrd — Thu, 16 Sep 2010 02:30:44 +0000

Note: the backslash-zero sequences (‘s; double backslash here (\\), hope that works …) disappeared in my and Tom’s comments.

By: enoksrd

enoksrd — Thu, 16 Sep 2010 02:28:08 +0000

Nice hack! But what I really wanted was to colorize the prompt, so that I could easily tell where long output (e.g. from :browse) started. I don’t understand why, but the sed trick doesn’t work for the prompt. But setting an ansi colored prompt in the ghci conf worked:

echo -e :set prompt ‘”33[32;1m%s33[34;1m>33[0m “‘ > ~/.ghc/ghci.conf

By: Martijn

Martijn — Thu, 24 Jun 2010 09:24:03 +0000

@Orphi Yes, I agree. It shouldn’t be too hard.

@Nikolas Good question. I have no good reason for it.

By: Nikolas Mayr

Nikolas Mayr — Wed, 03 Mar 2010 13:39:18 +0000

Why are you using

#!/usr/bin/env bash

intead of

#!/bin/bash

By: Orphi

Orphi — Mon, 01 Mar 2010 11:59:37 +0000

I still think GHCi should have this built-in. We already have ansi-terminal on Hackage, which does this in a [ahem] *portable* way. (Your examples don’t work on Windows, because it fails to grok ANSI escape sequences.)

By: Erlend

Erlend — Sat, 27 Feb 2010 18:12:54 +0000

Cool. Thanks!
Works perfectly on openSuse 11.2.

By: Tom Lokhorst

Tom Lokhorst — Sat, 27 Feb 2010 16:26:56 +0000

This is very useful!

I’ve updated the script to also highlight warnings (as I usually launch ghci from vim with -Wall):

#!/usr/bin/env bash

YELLOW=`echo -e ’33[93m’`
GREEN=`echo -e ’33[92m’`
RED=`echo -e ’33[91m’`
RESET=`echo -e ’33[0m’`

/usr/bin/ghci “${@}” 2>&1 |
sed “s/ Warning:/${YELLOW}&${RESET}/g;s/^Failed, modules loaded:/${RED}&${RESET}/g;s/^Ok, modules loaded:/${GREEN}&${RESET}/g”

I’m not happy with the fact that this merges the stdout and stderr, but I don’t know of a better way to do this.