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="$root/.toolchain/cabal"
+exec "$@"