Could Not Find Module `Data.Map' -- It Is A Member Of The Hidden Package


Answer :

These general steps were helpful for me to resolve similar issues:




  1. 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).



Hoogle result for Data.Map




  1. Open project-name.cabal in project root and add required package under build-depends:



    library
      hs-source-dirs:
          src

      build-depends:
          base >= 4.7 && < 5
        , containers

      exposed-modules:
          Lib

  2. Issue stack build to download and build dependencies



    (or stack ghci if you plan to use it in the REPL)




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.



Comments

Post a Comment

Popular posts from this blog

Converting A String To Int In Groovy

Answer : Use the toInteger() method to convert a String to an Integer , e.g. int value = "99".toInteger() An alternative, which avoids using a deprecated method (see below) is int value = "66" as Integer If you need to check whether the String can be converted before performing the conversion, use String number = "66" if (number.isInteger()) { int value = number as Integer } Deprecation Update In recent versions of Groovy one of the toInteger() methods has been deprecated. The following is taken from org.codehaus.groovy.runtime.StringGroovyMethods in Groovy 2.4.4 /** * Parse a CharSequence into an Integer * * @param self a CharSequence * @return an Integer * @since 1.8.2 */ public static Integer toInteger(CharSequence self) { return Integer.valueOf(self.toString().trim()); } /** * @deprecated Use the CharSequence version * @see #toInteger(CharSequence) */ @Deprecated public static Integer toInteger(String self) { return toInteg
Read more

"Cannot Create Cache Directory /home//.composer/cache/repo/https---packagist.org/, Or Directory Is Not Writable. Proceeding Without Cache"

Answer : if anyone pass through here, this is shorter solution: sudo chown -R $USER $HOME/.composer it seems to me the group information is missing in your command sudo chown -R <user> /home/<user>/.composer/cache/repo/https---packagist.org Shoud be sudo chown -R <user>:<group> /home/<user>/.composer/cache/repo/https---packagist.org But to avoid other permission issues, I would rather advise: sudo chown -R <user>:<group> /home/<user>/.composer/cache (you'll need access to other folders in there) and sudo chown <user>:<group> /home/<user>/.composer To make sure your user has permissions enough on the global composer folder. Mind the missing recursion so the user don't own keys created by root. If you need to find out the group: groups <user>
Read more

Android How Can I Convert A String To A Editable

Answer : As you probably found out, Editable is an interface so you cannot call new Editable() . However an Editable is nothing more than a String with Spannables, so use SpannableStringBuilder: Editable editable = new SpannableStringBuilder("Pass a string here"); If you only want to change the Spannables, never the text itself, you can use a basic SpannableString. Use Editable.Factory.getInstance().newEditable(str) From the android documentation: Returns a new SpannedStringBuilder from the specified CharSequence. You can override this to provide a different kind of Spanned.
Read more