#9995: :info enhancements -------------------------------------+------------------------------------- Reporter: shachaf | Owner: Type: feature request | Status: new Priority: normal | Milestone: Component: GHCi | Version: 7.8.4 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: None/Unknown | Unknown/Multiple Blocked By: | Test Case: Related Tickets: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- Old description:

`:info` is a very useful ghci command, but there are several improvements that could be made:

* It would be useful if `:i` showed not only which module a name is defined in, but which module(s) it was imported from in the current session. * A variant of `:i` that just prints a definition, rather than a definition and all instances, would be useful in many cases. E.g. `:i Show` prints the definition of `Show`, but then it prints so many instances that the definition is scrolled way off the screen. * `:i ->` is a parse error; it should behave like `:i (->)`, the way it works for other type-level operators. * hvr had some more suggestions: "finding out which package a module belongs to", "and what module an 'as'-alias is associated with". (Currently I think modules are out of `:info`'s scope, but perhaps it would be a useful addition.)

New description: `:info` is a very useful ghci command, but there are several improvements that could be made: 1. It would be useful if `:i` showed not only which module a name is defined in, but which module(s) it was imported from in the current session. 2. A variant of `:i` that just prints a definition, rather than a definition and all instances, would be useful in many cases. E.g. `:i Show` prints the definition of `Show`, but then it prints so many instances that the definition is scrolled way off the screen. 3. `:i ->` is a parse error; it should behave like `:i (->)`, the way it works for other type-level operators. 4. hvr had some more suggestions: "finding out which package a module belongs to", "and what module an 'as'-alias is associated with". (Currently I think modules are out of `:info`'s scope, but perhaps it would be a useful addition.) -- Comment (by simonpj): Sounds good to me. 1. I think this is pretty easy; this info is kept in the `GlobalRdrEnv`. Someone would have to figure out what to say if something was in scope in several different ways. 2. Even easier; but now you have to specify what the user should say to get the two different behaviours. Perhaps `:info` for the terse behaviour and `:info!` to add the instances? (Though that would be a change.) Oh, now I look I see that `:info!` is already used for something to do with instances. So maybe `:info`, `:info!`, and `:info!!`? Or we could drop instances altogether from `:info`, and instead have a new command `:instances T`. 3. Sounds plausible. "Just" a parser issue. 4. This is really `:info` for ''modules'', isn't it? So perhaps it's a variant of `:browse` (which tells you stuff about modules)? Anyway, if anyone wants to work on the specification, get agreement, and work on implementation, I can advise. Nothing technically difficult here I think. Simon -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9995#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler