Haskell back in awk's order of magnitude <_<

count.hs

-- Kevin Cantu
-- April 2012

import Control.Monad (when)
import Data.Map (Map)
import Data.List
import Data.List.Split
import qualified Data.Map as M
import System.Environment
import System.IO
import Text.CSV
import Text.Printf

-- read a CSV file
loadCSV path = 
   do
      eitherRecs <- parseCSVFromFile path
      let records = case eitherRecs
                    of Left e -> error . show $ e
                       Right recs -> recs
      return records

-- create a location map: (lat,lon) --> count
newMap :: Map String Integer
newMap = M.fromList []

-- increment a count
updateMap mm key = M.insertWith' (+) key 1 mm

-- read
readCoord line =
   case length fields
   of
      2 -> fields !! 1
      _ -> error "wrong size record: " ++ show line

   where
      fields = splitOn "," line
      
-- arg0 is the CSV file
getInputFile args =
   if length args == 1
   then args !! 0
   else error "usage: count csvInputFile"

-- logging
verbose = True
now xx = when verbose (putStrLn xx)

main =
   do
      args <- getArgs

      now "counting IPs per coordinate..."
      recs  <- readFile $ getInputFile args
      let coordsMap = foldl' updateMap newMap . map readCoord . lines $ recs

      now "saving/printing..."
      putStrLn . show $ coordsMap

      now "ok."