[Haskell] Re: ANNOUNCE: GHC version 6.10.3

[Claus Reinke]

>> More specifically, section "2.2.2 Moving GHC Around" indicates that
>> the entire GHC tree can be freely moved around "just by copying the
>> c:/ghc/ghc-version directory" (although it is necessary "to fix up the
>> links in 'Start/All Programs/GHC/ghc-version'" if this is done);
>> however, this information is not evident from the information provided
>> by the Windows installer.  This information initially led me to
>> conclude that uninstalling the previous version wasn't necessary to
>> upgrade; without this information, a new user may not be able to
>> determine whether uninstalling a previous version is necessary to
>> upgrade, and could make upgrading more confusing.
>
> I've added a section "Relocating a GHC installation" to the wiki:
>
> http://hackage.haskell.org/trac/ghc/wiki/Building/Installing#RelocatingaGHCinstallation

Relocation on Windows is currently slightly impeded if you're using
the Haskell Platform's GHC

http://trac.haskell.org/haskell-platform/ticket/19

> I think the rest could be solved by adding a note on the Windows section of the download page to 
> the effect that "This installer will not overwrite previous installed versions of GHC, with the 
> exception that the default handler for .lhs and .hs files will point to the latest installed 
> version".  Ian, would you like to add this to the download page?

For quite some time now, http://darcs.haskell.org/ghc/distrib/ghc.iss
has had this comment (in line with #916):

    ; this does _not_ follow the "play nice" proposal
    ; future version should

The current version will needlessly assign a different file type, leaving
Hugs in the cold (unless you install WinHugs last, which removes the
GHCi association..) and overwrite the handlers associated with ghc_haskell
(so if you want to use multiple versions of GHCi, you have to add them
back in manually).

See also:

    http://hackage.haskell.org/trac/ghc/ticket/916
    http://haskell.org/haskellwiki/Installers
    http://trac.haskell.org/haskell-platform/ticket/6#comment:12

The solution could be as simple as all distributors agreeing on a single
haskell file type (so that WinHugs won't switch out the Haskell Platform
bindings, and vice versa), and then not mangling the default "verbs" 'open'
and 'edit', but to use non-standard verbs  like open_with_GHCi-6.10.3,
so that Haskell installers add, rather than replace, functionality, as agreed
on in that haskellwiki page.

Works in Windows XP, and avoids Haskell installer ping-pong

    http://projects.haskell.org/pipermail/haskell-platform/2009-May/000154.html

The MSDN docs seem to be in upheaval at the moment, so I can't
verify that this [1] was the most useful documentation link - I think that,
before Windows XP, there was no support for non-standard verbs, so
on older Windows versions, the current bad system might have to be
used as a fallback, but that is no reason to use it on current versions,
several years after agreement):

Claus

[1] 
http://msdn.microsoft.com/library/en-us/shellcc/platform/shell/programmersguide/shell_basics/shell_basics_extending/fileassociations/fa_intro.asp

[2] http://blogs.msdn.com/oldnewthing/archive/2007/04/30/2332224.aspx
        'The default verb is not necessarily "open"'