first

apps/multi-ghc.nix

@@ -0,0 +1,27 @@
+{ pkgs     ? import <nixpkgs> {},
+  versions ? [ "8.10" "9.0" "9.2" "9.4" "9.6" "9.8" "9.10" "9.12" ],
+}:
+let
+  inherit (builtins) attrValues replaceStrings;
+  inherit (pkgs)     lib stdenv haskell;
+
+  toPkg = version:
+    "ghc" + replaceStrings ["."] [""] version;
+
+  ghcs = lib.genAttrs versions
+    (v: haskell.compiler.${toPkg v});
+
+  mkLinkCmd = version: pkg: ''
+    ln -s ${pkg}/bin/ghc $out/bin/ghc-${version}
+    ln -s ${pkg}/bin/ghci $out/bin/ghci-${version}
+    ln -s ${pkg}/bin/ghc-pkg $out/bin/ghc-pkg-${version}
+  '';
+in
+stdenv.mkDerivation {
+  name         = "multi-ghc";
+  buildInputs  = attrValues ghcs;
+  dontUnpack   = true;
+  installPhase = lib.concatLines
+    ([ "mkdir -p $out/bin" ] ++
+     lib.mapAttrsToList mkLinkCmd ghcs);
+}