Could not find module `Data.Map' -- It is a member of the hidden package
The reason you can import Data.Char
and Data.List
is that they are part of the package base
, which is included with GHC and is always loaded with GHCi. By contrast, Data.Map
is in the external library containers
. One way to load it with stack ghci
is to add a cabal file with a build-depends
on containers
. This will install it in the stack environment for xxxx
, so it will then be accessible.
These general steps were helpful for me to resolve similar issues:
Use Hoogle or Stackage to find the package where the module resides
Note that Hoogle and Stackage are case-sensitive. Looking up
Data.Map
in Hoogle yields a list similar to the one below. Stackage has a slightly different style, but the basics are the same (mostly because it also uses Hoogle for lookup).
The lines in green under the result headings show the name(s) of the containing
(1) package(s) (in small caps) and
(2) module(s) (capitalized).
Open
project-name.cabal
in project root and add required package underbuild-depends:
library hs-source-dirs: src build-depends: base >= 4.7 && < 5 , containers exposed-modules: Lib
Issue
stack build
to download and build dependencies(or
stack ghci
if you plan to use it in the REPL)