restricted_to :: VersionMap -> [PackageName] -> VersionMap
restricted_to v packages = filter (go . fst) v
  where
    go :: PackageName -> Bool
    go = (`elem` packages)
restricted_to :: VersionMap -> [PackageName] -> VersionMap
restricted_to v packages = filter (go . fst) v
  where
    go :: PackageName -> Bool
    go = (`elem` packages)
restricted_to v packages = filter (go . fst) v
  where
    go :: PackageName -> Bool
    go = (`elem` packages)