Is there a way to see the list of functions in a module, in GHCI?

Question

I find it handy in Python or Common Lisp that you can list a library's contents at runtime. Does Haskell have the same thing, in particular from a GHCI prompt?

Cruiser

Answer 1

GHCi has a :browse command to list the contents of modules:

Prelude> :browse Data.List
(\\) :: (Eq a) => [a] -> [a] -> [a]
delete :: (Eq a) => a -> [a] -> [a]
deleteBy :: (a -> a -> Bool) -> a -> [a] -> [a]
deleteFirstsBy :: (a -> a -> Bool) -> [a] -> [a] -> [a]
elemIndex :: (Eq a) => a -> [a] -> Maybe Int
...
Prelude> :help                    
...
   :browse[!] [[*]<mod>]       display the names defined by module <mod>
                               (!: more details; *: all top-level names)
...

Chaucerian

Answer 2

Depending on exactly what information you intend to extract... If your version of GHCi supports tab-completion, then you can use that to list all of a namespace's available functions:

Prelude> :m +Data.List
Prelude Data.List> Data.List.<PRESS TAB KEY HERE>
Display all 109 possibilities? (y or n) <PRESS n>
Prelude Data.List> Data.List.un<PRESS TAB KEY HERE>
Data.List.unfoldr  Data.List.unlines  Data.List.unzip3   Data.List.unzip6   
Data.List.union    Data.List.unwords  Data.List.unzip4   Data.List.unzip7   
Data.List.unionBy  Data.List.unzip    Data.List.unzip5   

Ladylove

In current ghci(s) :m +Data.List its deprecated. – Kinder

@Kinder what's the undeprecated thing to do? – Speckle

@Speckle As far as I know, the old syntax is not deprecated. However, there is some recently added alternative syntax: the familiar import statements allowed in modules are also allowed in ghci. So one could also write import Data.List. I suspect EliuX knew about the addition of this syntax to ghci and assumed that the old syntax was deprecated, but I don't believe that to be correct. Indeed, there is no import statement that has the same effect as ghci's :m * syntax, which is frequently used (even if only implicitly), so it would be surprising indeed for :m to be deprecated. – Dhoti