HS_DIR=/usr/share/haskell/haskell-x11

post_install() {
  ${HS_DIR}/register.sh 
}

pre_upgrade() {
  ${HS_DIR}/unregister.sh &>/dev/null # it whines uselessly about deps 
}

post_upgrade() {
  ${HS_DIR}/register.sh 
}

pre_remove() {
  ${HS_DIR}/unregister.sh 
}