= Access a Haskell library package in the nixpkgs repo (without a `.cabal` file)

////
$ mkdir tempwork
$ cd tempwork
$ cp ../flake.nix ../Main.hs .
$ git add flake.nix
$ nix develop
$ git add flake.lock
$ git commit -a -m temp
////

Occasionally you might want to run a short Haskell program that depends on a Haskell library,
but you don't want to bother writing a cabal file.

Example: Access the `containers` package from the `haskellPackages` set in the nixpkgs repo.

[source,nix,linenums,highlight='11,16']
.flake.nix
....
include::flake.nix[]
....

Here's a short Haskell program that uses it.

[source,haskell,linenums]
.Main.hs
....
include::Main.hs[]
....

Here's a demonstration using the program.

....
$# ../../../../../start-shell nix develop <<EOL
$ runghc Main.hs
$# EOL
....

////
Good adoc0 scripts clean up after themselves.
$ cd .. ; rm -rf tempwork # clean up
////