#5850: Greater customization of GHCi prompt
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Reporter: JamesFisher | Owner:
Type: feature request | Status: new
Priority: normal | Component: GHCi
Version: 7.4.1 | Keywords:
Os: Unknown/Multiple | Architecture: Unknown/Multiple
Failure: None/Unknown | Testcase:
Blockedby: | Blocking:
Related: |
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GHCi is bit more than a Haskell interpreter. With the {{{:!}}} and
{{{:cd}}} commands, we have trivial access to the shell, making it often
unnecessary to leave GHCi. For this reason GHCi has become my *de facto*
primary shell.
The GHCi prompt therefore needs to show a bit more than just Haskell
information. Most importantly, the current working directory is often
important to me.
[http://www.haskell.org/ghc/docs/7.4.1/html/users_guide/ghci-commands.html
We can indeed customize the GHCi prompt] using {{{:set prompt}}}. This
takes the form of a string with a single escape sequence: {{{%s}}}, which
is replaced with a list of currently loaded modules.
Most shells allow arbitrary user customization of the prompt. The
{{{bash}}} prompt has [http://tldp.org/HOWTO/Bash-Prompt-HOWTO/bash-
prompt-escape-sequences.html numerous escape sequences for useful
information], and if those aren't enough, it allows [http://tldp.org/HOWTO
/Bash-Prompt-HOWTO/x279.html arbitrary command calls].
GHCi should gain similar customization abilities. Ways to implement this
may include:
1. addition of more escape sequences, like {{{%pwd}}}.
2. addition of a single extra escape sequence with one parameter (an
external command call), like like {{{%call(pwd --logical)}}}.
3. redesigning the {{{:set prompt}}} option to take not a {{{String}}} but
a Haskell function, like {{{[Module] -> IO String}}}.
Option 2 would probably have the best power-to-simplicity ratio.
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/5850>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
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