[Haskell-cafe] How to cabal fetch mtl==

Iain Alexander ia at stryx.demon.co.uk
Thu Nov 25 02:52:09 CET 2010

F:\Util\Haskell>cabal fetch mtl==
Resolving dependencies...
cabal: internal error: could not construct a valid install plan.
The proposed (invalid) plan contained the following problems:
The following packages are involved in a dependency cycle transformers-,
special-functors-1.0, mtl-

F:\Util\Haskell>cabal -V
cabal-install version 0.8.2
using version of the Cabal library

Could someone please remind me of the correct incantation to make this work.  

(I observe that transformers- optionally (by cabal flag) depends on 
special-functors, and special-functors-1.0 depends on mtl.  So given that mtl-2 
no doubt depends on transformers, I can see the potential for confusion, but 
there presumably must be a way of breaking the (apparent) loop.)  

Iain Alexander      ia at stryx.demon.co.uk

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