[Haskell-cafe] Why so many strings in Network.URI, System.Posix and similar libraries?

10 Mar 2012

      The content of URIs is defined in terms of octets in the RFC,
and all Posix interfaces are byte streams and C strings, not
character strings. Yet in Haskell, we find these objects exposed
with String interfaces:
...
:info Network.URI.URI
data URI
  = URI {uriScheme :: String,
         uriAuthority :: Maybe URIAuth,
         uriPath :: String,
         uriQuery :: String,
         uriFragment :: String}
        -- Defined in Network.URI
...
:info System.Posix.Env.getEnvironment
System.Posix.Env.getEnvironment :: IO [(String, String)]
        -- Defined in System.Posix.Env
But there is no law that environment variables must be made of
characters:

 :; export x=$'\xFF' ; echo -n $x | xxd -p
  ff
 :; locale
  LANG="en_US.UTF-8"

That the relationship between bytes and characters can be
confusing, both in working with UNIX and in dealing with web
protocols, is undeniable -- but it seems unwise to limit the
options available to Haskell programmers in dealing with these
systems.

--
Jason Dusek
pgp // solidsnack // C1EBC57DC55144F35460C8DF1FD4C6C1FED18A2B