init

common-types.hs

@@ -0,0 +1,11 @@
+main =
+  do
+    putStrLn ("hask" ++ "ell")
+
+    putStrLn ("1+1 = " ++ show (1 + 1))
+
+    putStrLn ("7.0/3.0 = " ++ show (7.0 / 3.0))
+
+    putStrLn (show (True && False))
+    putStrLn (show (True || False))
+    putStrLn (show (not True))

default.nix

@@ -0,0 +1,18 @@
+rec {
+
+  versions = import ./versions.nix;
+
+  pkgs = import versions.nixpkgs {};
+
+  inherit (pkgs) callPackage haskellPackages;
+
+  ghc = haskellPackages.ghcWithPackages (p: [
+    p.bytestring
+    p.text
+  ]);
+
+  inherit (haskellPackages) ghcid;
+
+  outputs = callPackage ./outputs.nix { inherit ghc; };
+
+}

hello-world.hs

@@ -0,0 +1 @@
+main = putStrLn "hello world"

outputs.nix

@@ -0,0 +1,21 @@
+{ runCommand, linkFarm, ghc }:
+
+let
+  run = name: hsFile:
+    {
+      name = "${name}.txt";
+      path = runCommand "phrasebook-output-${name}.txt"
+        {
+          buildInputs = [ ghc ];
+          inherit hsFile;
+        }
+        ''
+          runhaskell "$hsFile" > $out
+        '';
+    };
+
+in
+
+  linkFarm "haskell-phrasebook-outputs" [
+    (run "hello-world" ./hello-world.hs)
+  ]

readme.md

@@ -0,0 +1,35 @@
+# The Haskell Phrasebook
+
+https://typeclasses.com/phrasebook
+
+## Using Nix shell
+
+1. [Install Nix][install]
+
+2. Enter a Nix shell:
+
+    ```
+    $ nix-shell --pure
+    ```
+
+3. Within the Nix shell, you have all of the dependencies required by the examples in the Phrasebook. You can run commands such as:
+
+    ```
+    $ runhaskell hello-world.hs
+    hello world
+    ```
+    
+    ```
+    $ ghcid --command 'ghci hello-world.hs'
+    
+    ``` 
+
+## Nix dependency versions
+
+The `update-versions` script updates the dependency hashes in `versions.json` to their latest commits. The JSON data is then used by `versions.nix`. This system is described in Vaibhav Sagar's blog post, [*Quick and Easy Nixpkgs Pinning*][vaibhav].
+
+  [install]:
+    https://nixos.org/nix/manual/#chap-installation
+
+  [vaibhav]:
+    https://vaibhavsagar.com/blog/2018/05/27/quick-easy-nixpkgs-pinning/

shell.nix

@@ -0,0 +1,4 @@
+let
+  inherit (import ./default.nix) pkgs ghc ghcid;
+in
+  pkgs.mkShell { buildInputs = [ ghc ghcid ]; }

update-versions

@@ -0,0 +1,27 @@
+#! /usr/bin/env nix-shell
+#! nix-shell -i bash
+#! nix-shell -p curl jq nix
+
+set -eufo pipefail
+
+function update {
+  FILE=$1
+  PROJECT=$2
+  BRANCH=${3:-master}
+
+  OWNER=$(jq -r '.[$project].owner' --arg project "$PROJECT" < "$FILE")
+  REPO=$(jq -r '.[$project].repo' --arg project "$PROJECT" < "$FILE")
+
+  REV=$(curl "https://api.github.com/repos/$OWNER/$REPO/branches/$BRANCH" | jq -r '.commit.sha')
+  SHA256=$(nix-prefetch-url --unpack "https://github.com/$OWNER/$REPO/archive/$REV.tar.gz")
+  TJQ=$(jq '.[$project] = {owner: $owner, repo: $repo, rev: $rev, sha256: $sha256}' \
+    --arg project "$PROJECT" \
+    --arg owner "$OWNER" \
+    --arg repo "$REPO" \
+    --arg rev "$REV" \
+    --arg sha256 "$SHA256" \
+    < "$FILE")
+  [[ $? == 0 ]] && echo "${TJQ}" >| "$FILE"
+}
+
+update versions.json nixpkgs nixos-19.03

versions.json

@@ -0,0 +1,8 @@
+{
+  "nixpkgs": {
+    "owner": "NixOS",
+    "repo": "nixpkgs-channels",
+    "rev": "314775040bb5e32101458f3afe93bfc0e0591112",
+    "sha256": "1scq233g7vcw6v6axc1ga19a0q1b6bj8qy76pmc76d2bafhrvjrn"
+  }
+}

versions.nix

@@ -0,0 +1,11 @@
+let
+  inherit ((import <nixpkgs> { }).lib) mapAttrs;
+  inherit (builtins) fetchTarball fromJSON readFile;
+
+  fetchFromGitHub = { owner, repo, rev, sha256 }:
+    builtins.fetchTarball {
+      inherit sha256;
+      url = "https://github.com/${owner}/${repo}/archive/${rev}.tar.gz";
+    };
+in
+  mapAttrs (_: fetchFromGitHub) (fromJSON (readFile ./versions.json))