On Thu, Nov 25, 2010 at 2:52 AM, Iain Alexander
<log> F:\Util\Haskell>cabal fetch mtl==2.0.0.0 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-0.2.2.0, special-functors-1.0, mtl-2.0.0.0
F:\Util\Haskell>cabal -V cabal-install version 0.8.2 using version 1.8.0.2 of the Cabal library </log>
Could someone please remind me of the correct incantation to make this work.
(I observe that transformers-0.1.4.0 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.)
TIA, Iain. -- Iain Alexander ia@stryx.demon.co.uk
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Maybe it helps if special-functors gets an upper bound on its mtl dependency: mtl < 2. BTW what is you ghc --version? Because I have no problems fetching mtl-2: $ ghc --version The Glorious Glasgow Haskell Compilation System, version 6.12.1 $ cabal --version cabal-install version 0.8.0 using version 1.8.0.2 of the Cabal library $ cabal fetch mtl==2.0.0.0 Resolving dependencies... Downloading mtl-2.0.0.0... Regards, Bas