[Haskell-cafe] Re: Completely confused by cabal

[Achim Schneider]

Colin Paul Adams <colin at colina.demon.co.uk> wrote:

>     Achim> uh... because you're a mere user and don't have the rights
>     Achim> to do so?
> 
> No, I own the machine.
>
Well, but it neither knows nor cares, unless you log in as root.
"colin" isn't allowed to write to /usr/local/lib/ghc-6.11.20090319/ .
root's and colin's home directories are distinct, as well, that's why
both need to do cabal update to install stuff: Users can't read root
(or any other user's) home directories; root could read colin's home
directory, but musn't trust any data in it, as colin could use that
trust to weasel root access.

> I can't. It doesn't provide up-to-date ghc and things.
> 
<insert snappy switch-to-gentoo comment here>

>     Achim> programs with your user account, inside your home
>     Achim> directory, is perfectly acceptable (and traditional) under
>     Achim> unix.
> 
> But it means I have to install everyhting twice - once as --user, once
> as --global.
>
No, you don't, the database ghc uses to compile stuff is a union of
both databases, user installs overriding global installs. Assuming that
you're the machine's only user, you only ever need to install stuff as
that user:

ksf at solaris ~ % ghc-pkg list
/usr/lib64/ghc-6.10.1/./package.conf:
    Cabal-1.6.0.1, HTTP-3001.1.4, QuickCheck-1.2.0.0,
    QuickCheck-2.1.0.1, X11-1.4.4, X11-xft-0.3, array-0.2.0.0,
    base-3.0.3.0, base-4.0.0.0, binary-0.4.4, bytestring-0.9.1.4,
    cairo-0.10.0, containers-0.2.0.0, directory-1.0.0.2,
    editline-0.2.1.0, filepath-1.1.0.0, filepath-1.1.0.1, gconf-0.10.0,
    (ghc-6.10.1), ghc-paths-0.1.0.5, ghc-prim-0.1.0.0, glade-0.10.0,
    glib-0.10.0, gtk-0.10.0, gtkglext-0.10.0, gtksourceview2-0.10.0,
    haddock-2.4.1, haskell-src-1.0.1.3, haskell98-1.0.1.0, hpc-0.5.0.2,
    html-1.0.1.2, integer-0.1.0.0, mozembed-0.10.0, mtl-1.1.0.2,
    network-2.2.0.1, old-locale-1.0.0.1, old-time-1.0.0.1,
    packedstring-0.1.0.1, parsec-3.0.0, pretty-1.0.1.0,
    process-1.0.1.0, random-1.0.0.1, readline-1.0.1.0,
    regex-base-0.93.1, regex-compat-0.92, regex-posix-0.93.2, rts-1.0,
    soegtk-0.10.0, stm-2.1.1.2, svgcairo-0.10.0, syb-0.1.0.0,
    template-haskell-2.3.0.0, unix-2.3.1.0, utf8-string-0.3.3,
    zlib-0.5.0.0
/home/ksf/.ghc/x86_64-linux-6.10.1/package.conf:
    MemoTrie-0.4.3, bytestring-mmap-0.2.0, bytestring-trie-0.1.4,
    extensible-exceptions-0.1.1.0, ipprint-0.3, iteratee-0.1.1,
    mmap-0.2, regex-posix-0.72.0.3

I basically did emerge cabal-install to bootstrap my installation, then
emerge gtk2hs as it's not available via hackage. Then, I install what
I need to hack as user using cabal install. (I recently nuked my
~/.cabal and ~/.ghc, that's why the user database is that small).

Installing ghc as user works equally well.

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