Error while installing new packages with GHC 7.4.1

[Albert Y. C. Lai]

On 12-02-29 06:04 AM, Antoras wrote:
> I don't know where the dependency to array-0.3.0.3 comes from. Is it
> possible to get more info from cabal than -v?

hoogle-4.2.8 has "Cabal >= 1.8 && < 1.13", this brings in Cabal-1.12.0.

Cabal-1.12.0 has "array >= 0.1 && < 0.4", this brings in array-0.3.0.3.

It is a mess to have 2nd instances of libraries that already come with 
GHC, unless you are an expert in knowing and avoiding the treacherous 
consequences. See my
http://www.vex.net/~trebla/haskell/sicp.xhtml

It is possible to fish the output of "cabal install --dry-run -v3 
hoogle" for why array-0.3.0.3 is brought in. It really is fishing, since 
the output is copious and of low information density. Chinese idiom: 
needle in ocean (haystack is too easy). Example:

"selecting hoogle-4.2.8 (hackage) and discarding Cabal-1.1.6, 1.2.1, 
1.2.2.0,
1.2.3.0, 1.2.4.0, 1.4.0.0, 1.4.0.1, 1.4.0.2, 1.6.0.1, 1.6.0.2, 1.6.0.3,
1.14.0, blaze-builder-0.1, case-insensitive-0.1,"

We see that selecting hoogle-4.2.8 causes ruling out Cabal 1.14.0

Similarly, the line for "selecting Cabal-1.12.0" mentions ruling out 
array-0.4.0.0