parse algebraic declarations and ordered match clauses

scripts/env

@@ -0,0 +1,6 @@
+#!/bin/sh
+set -eu
+root=$(CDPATH= cd -- "$(dirname -- "$0")/.." && pwd)
+export PATH="$root/.toolchain/bin:$root/.toolchain/ghc-bin:$PATH"
+export CABAL_DIR="$root/.toolchain/cabal"
+exec "$@"

scripts/setup

@@ -0,0 +1,20 @@
+#!/bin/sh
+set -eu
+root=$(CDPATH= cd -- "$(dirname -- "$0")/.." && pwd)
+cd "$root"
+mkdir -p .toolchain/bin .toolchain/ghc-bin .toolchain/cabal
+if [ ! -x .toolchain/bin/cabal ]; then
+  curl -fL https://downloads.haskell.org/~cabal/cabal-install-3.0.0.0/cabal-install-3.0.0.0-x86_64-unknown-linux.tar.xz -o .toolchain/cabal.tar.xz
+  tar xf .toolchain/cabal.tar.xz -C .toolchain/bin
+  rm .toolchain/cabal.tar.xz
+fi
+ghc_bin=/home/rack/.ghcup/ghc/8.6.5/bin
+for tool in ghc ghc-pkg ghci runghc haddock hsc2hs hpc; do
+  ln -sf "$ghc_bin/$tool" ".toolchain/ghc-bin/$tool"
+done
+if [ ! -f .toolchain/cabal/config ]; then
+  printf -- '-- isolated cabal configuration for the pinned historical toolchain\n-- no remote repository is configured because only GHC boot libraries are used\n' > .toolchain/cabal/config
+fi
+./scripts/env ghc --version
+./scripts/env cabal --version
+./scripts/env cabal v1-build