我怎样才能解决这个问题？
$ cabal install http-conduit
Resolving dependencies...
cabal: Could not resolve dependencies:
trying: attoparsec-0.13.0.1/installed-5b6... (user goal)
trying: http-conduit-2.1.8 (user goal)
trying: monad-control-1.0.0.5 (dependency of http-conduit-2.1.8)
next goal: conduit (dependency of http-conduit-2.1.8)
rejecting: conduit-1.2.6.1, 1.2.6, 1.2.5.1, 1.2.5, 1.2.4.3, 1.2.4.2, 1.2.4.1,
1.2.4, 1.2.3.1 (conflict: attoparsec =>
transformers==0.5.1.0/installed-426..., conduit => transformers>=0.2.2 &&
<0.5)
rejecting: conduit-1.2.3, 1.2.2.2, 1.2.2.1, 1.2.2, 1.2.1, 1.2.0.2, 1.2.0.1,
1.2.0, 1.1.7, 1.1.6, 1.1.5, 1.1.4, 1.1.3, 1.1.2.1, 1.1.2, 1.1.1.1, 1.1.1,
1.1.0.2, 1.1.0.1, 1.1.0, 1.0.17.1, 1.0.17, 1.0.16, 1.0.15.1, 1.0.15, 1.0.14,
1.0.13.1, 1.0.13, 1.0.12, 1.0.11.1, 1.0.11, 1.0.10.1, 1.0.10, 1.0.9.3,
1.0.9.2, 1.0.9.1, 1.0.9, 1.0.8, 1.0.7.4, 1.0.7.3, 1.0.7.2, 1.0.7.1, 1.0.7,
1.0.6, 1.0.5.1, 1.0.5, 1.0.4.2, 1.0.4.1, 1.0.4, 1.0.3, 1.0.2, 1.0.1, 1.0.0.2,
1.0.0.1, 1.0.0, 0.5.6, 0.5.5 (conflict: monad-control==1.0.0.5, conduit =>
monad-control>=0.3.1 && <0.4)
rejecting: conduit-0.5.4.2, 0.5.4.1, 0.5.4, 0.5.3, 0.5.2.7, 0.5.2.6, 0.5.2.5,
0.5.2.4, 0.5.2.3, 0.5.2.2, 0.5.2.1, 0.5.2, 0.5.1, 0.5.0, 0.4.2, 0.4.1.1,
0.4.1, 0.4.0.1, 0.4.0, 0.3.0, 0.2.2, 0.2.1, 0.2.0, 0.1.1.1, 0.1.1, 0.1.0,
0.0.4, 0.0.3, 0.0.2, 0.0.1.1, 0.0.1, 0.0.0.2, 0.0.0.1, 0.0.0 (conflict:
http-conduit => conduit>=0.5.5 && <1.3)
Backjump limit reached (change with --max-backjumps).
Note: when using a sandbox, all packages are required to have consistent
dependencies. Try reinstalling/unregistering the offending packages or
recreating the sandbox.
和
$ cabal --version
cabal-install version 1.22.8.0
using version 1.22.7.0 of the Cabal library
答案 0 :(得分：0)
The issue was that conduit required an older version of transformers than the one at the base of your dependency tree.
Since then, a newer conduit has been uploaded that lifts the upper bound: http://hackage.haskell.org/package/conduit-1.2.6.2
现在，如果你尝试相同的程序，那么应该工作......