Output dependency versions for cabal sandbox.

cabal-freeze.hs

#!/usr/bin/env runghc                                                           
                                                                                
import Data.Tuple                                                               
import System.Process                                                           
                                                                                
main = do                                                                       
    out <- getBash "ls .cabal-sandbox/lib/*"                                    
    let packages = lines out                                                    
    let packageVersions = map (tjoin "==" . splitVersion) packages              
    putStrLn . unlines $ packageVersions                                        
                                                                                
getBash cmd = readProcess "bash" ["-c", cmd] ""                                 
splitOn p = fmap (drop 1) . break p                                             
splitVersion = swap . tmap reverse . splitOn (=='-') . reverse                  
tmap f (x, y) = (f x, f y)                                                      
tjoin s (x, y) = x ++ s ++ y

cabal-freeze.py

#!/usr/bin/env python

import commands
import re

out = commands.getoutput('ls .cabal-sandbox/lib/*')
packages = out.split('\n')
package_names = [re.split(r'\-\d\.', x, maxsplit=1)[0] for x in packages]
package_map = zip(package_names, packages)
version_map = [(k, v[len(k)+1:]) for k, v in package_map]
result = '\n'.join("{}=={}".format(k, v) for k, v in version_map)
print result