Folks, Dean Herington suggested another possible syntax for the :module command. To paraphrase, the new syntax would be: :m [+|-] [*]M1 ... [*]Mn (n >= 0) Using the convention that [] indicates an optional syntactic element, '|' indicates choice, and M1 ... Mn are module names. - with no +/-, the command sets the scope - with +, the indicated modules are added to the scope - with -, the indicated modules are removed from the scope - 'M' means include the full top-level scope of module M - '*M' means include just the exports of module M Currently the non-* form isn't supported for compiled modules, and attempting to set an unsupported scope results in an error. I think this is simpler than the original suggestion, although it makes some cases erroneous where the previous form would "do the right thing". Eg. Now you have to say ':m + *IO' to import IO, whereas previously you could just say ':m +IO'. I think I'd probably ":def :import (return . (":m + *" ++))". On the other hand, the new form separates what is really just an implementation restriction (that we can't load the top-level scope of a compiled module) from the user interface, which is a good thing. At some point we might lift the restriction, which we could do without changing the meaning of the :m command. Unless anyone has any more suggestions or objections, I'm inclined to go with this syntax. Cheers, Simon
-----Original Message----- From: Dean Herington [mailto:heringto@cs.unc.edu] Sent: 09 January 2002 15:59 To: Simon Marlow Cc: GHC Users Mailing List Subject: Re: GHC Poll: scope in GHCi
A minor suggestion: Let ":m *M" apply to compiled modules as well as interpreted. In other words, ":m +M" requests all top-level entities (accepting only exported ones for compiled modules) while ":m *M" requests only exported entities (whether the module is compiled or interpreted).
More generally, though, I dislike allying the "all / exported only" choice with the "add a module to the scope" command; they should be specified independently. In particular, one should be able to make the choice for each of the modules in the ":m M1..Mn" command. (Otherwise, how can one reasonably request a scope consisting of only the exported entities from a single interpreted module?)
A question: What is the syntax of the "M1..Mn" form?
I like Koen Claessen's suggestion that one be able to request all top-level names from a compiled module.
Here's a variant of Simon's proposal that addresses the above concerns:
* Let a <mods> be either the name of a module (implying the set of all top-level names in that module) or a square-bracketed, space-separated list of module names (implying the set of names exported from the modules).
* Let a <modslist> be a list of <mods>s. Whitespace must separate adjacent <mods>s when neither is in square brackets.
* Let the ":module" command take an optional '+' or '-' followed by a <modslist>. '+' indicates additions to the scope; '-' indicates subtractions from the scope; absence of both indicates redefinition of the scope.
Square bracketing is suggested for indicating that only exported names are desired, to match the prompt syntax. An alternative for both would be to prefix each such module name by, say, '*'. Examples of these two alternatives:
Main[IO]> :module + [Char Monad] Foo Main Foo[IO Char Monad]>
or
Main *IO> :module + *Char *Monad Foo Main *IO *Char *Monad Foo>
I think I prefer the latter.
Dean