[Haskell-cafe] Re: wanted: haskell one-liners (in the perl senseof one-liners)

Claus Reinke claus.reinke at talk21.com
Sun Mar 4 18:45:28 EST 2007

>I think I could have most of the oneliner goodness of h4sh, without having to do 
>the module install, if I could figure out a way to include modules with ghc -e.

i confess myself to be among those who underappreciated ghc -e, until this thread:)

as Joachim said (thanks for starting this, btw;-), we can use qualified names

    $ echo hello world | hmap 'map Char.toUpper'

and to get at your other methods, the question is not how to include modules
with ghc -e; instead, recall that ghc -e supplies a command to be evaluated
within the context of its parameter module (single input for a ghci session):

    $ cat Imports.hs
    import Debug.Trace
    helper x = trace "hi there" (x+1)

    $ ghc -e 'helper 41' Imports.hs
    hi there

as to the original question in this thread, my .bashrc now also has a few less
symmetric entries:

           function hrunl { ghc -e "interact(show.($*).lines)";  }
           function hrunw { ghc -e "interact(show.($*).words)";  }
           function hrunwl { ghc -e "interact(show.($*).map words.lines)";  }

using which the one-liner becomes something like

    find -maxdepth 1 -type f | xargs du | hrunwl "sum . map (read . head)"

(the find/du is better left in shell tool land, it seems, and default Num is Integer)


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