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Diffstat (limited to 'haskell/cabal-lib.html')
| -rw-r--r-- | haskell/cabal-lib.html | 20 |
1 files changed, 3 insertions, 17 deletions
diff --git a/haskell/cabal-lib.html b/haskell/cabal-lib.html index 90bab1c..9f93c19 100644 --- a/haskell/cabal-lib.html +++ b/haskell/cabal-lib.html @@ -46,7 +46,7 @@ ghci> print "hi" Variable not in scope: print :: base-4.17.2.0:GHC.Base.String -> t ghci> </code></pre> -<p>I mean, that doesn't look good, doesn't it?</p> +<p>I mean, that doesn't look good, does it?</p> <p>And if that did not scare you enough, suppose that in the future, you want to use a newer version of <code>brick</code> and try to install that using <code>cabal install --lib brick</code> again. What you'll see is this:</p> <pre><code>$ cabal install --lib brick-1.9 @@ -56,22 +56,8 @@ may break other packages. Use --force-reinstalls to proceed anyway. Packages: brick </code></pre> <p>(I simulated the situation by installing an older version instead. I can't time-travel, unfortunately.)</p> -<p>Or suppose that you now also want to use another library, say <code>eigen</code>:</p> -<pre><code>$ cabal install --lib eigen -Resolving dependencies... -Error: cabal: Could not resolve dependencies: -[__0] next goal: brick (user goal) -[__0] rejecting: -brick-1.10/installed-1f76dfaf75736c0f6e2a4a2cf992bb12da05f6bbc7985f9787547739947e4696 -(package is broken, missing dependency -bimap-0.5.0-2ee7565ca29f0edc78a3c8fe09c9eef36c96d08473660eec8a944cef16ac4d86) -[__0] trying: brick-1.10 -[__1] trying: vty-5.39 (dependency of brick) -... -... -</code></pre> -<p>The error message is much longer than this, but I cut it off to save some space. -Apparently it claims our installation of <code>brick</code> is actually broken, despite it working okay in <code>ghci</code>, but in any case this didn't work.</p> +<p>Another thing that would fail is trying to install a package that is incompatible with the versino of <code>brick</code> you have now "installed". +I don't have a good example for this post because I couldn't find a neat pair of incompatible packages that didn't have many other dependencies, but I hope you'll trust me that this will result in the well-known (to seasoned haskellers) cabal dependency resolution errors.</p> <h2>What happened?</h2> <p>Note the line printed by <code>ghci</code>:</p> <pre><code>Loaded package environment from /home/tom/.ghc/x86_64-linux-9.4.7/environments/default |