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From: andreatta@mail.chem.sc.edu (Dan Andreatta)
Newsgroups: comp.lang.ada
Subject: Re: Ada Popularity: Comparison of Ada/Charles with C++ STL (and Perl)
Date: 24 Sep 2004 10:40:56 -0700
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 <338040f8.0409230912.70e3375b@posting.google.com> <u6564dfge.fsf@obry.org>
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Date: 2004-09-24T10:40:56-07:00
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Pascal Obry <pascal@obry.org> wrote in message news:<u6564dfge.fsf@obry.org>...
> andreatta@mail.chem.sc.edu (Dan Andreatta) writes:
> 
> > And I write it in Haskell. 14 lines. OK, I cheated, I used GHC libraries.
> 
> And it is just unreadable ! I just can't understand how this is supposed
> to work!
> 
> Pascal.

I understand. Functional languages require a change in prospective.
But also I made unreadable to have a less lines :-). Hope now you find
it more readable.

Here is slightly rewritten:

module Main where

import Data.FiniteMap
import Data.List
import System
import Char

count_words :: [String] -> [(String, Integer)]
count_words ws = wc
    where
    comp (_,n) (_,m) = compare m n -- used in sortBy to sort 
                                   -- the values, not keys
    ws' = zip ws [1,1..] -- creates a list [("word",1),("word",1)...]
    -- In functional languages the hash table is substituted with a
    -- finite map
    -- emptyFM creates an empty finite map
    -- addToFM adds an element in the form (key, value) to a
    --   finite map. If the element already exists,
    --   it is replaced by the new one.
    -- addListToFM adds a list of elements, 
    --   [(key, value), (key, value)...]
    -- addListToFM_C instead applies an operation (e.g. +) between 
    --   the values of the old and new elements with the same key.
    --   Since every key has value 1,
    --   we count the number of keys in the list.
    fm  = addListToFM_C (+) emptyFM  ws'
    list = fmToList fm -- Creates a list from the finite map in the
                       -- form [(key,value)], with the keys ordered.
    wc = sortBy comp list -- sort the list in ascending order
                          -- of the values.

-- this to take care of alphanumeric symbols.
-- Replace them with spaces.
removeSymbol x = if isAlphaNum x then x else ' '
 
main = do
       args <- getArgs   -- get the command line arguments as
                         -- a list of strings.
       f <- readFile (args!!0) -- the first one is the one we want. 
                               -- And read the whole file and
                               -- return a String
       let f1 = map (removeSymbol.toLower) f 
                       -- convert to lowercase and substitue spaces
                       -- for symbols. For every character, convert
                       -- it to lowercase and remove it if a symbol
       let f2 = words f1 -- divide the string in a list of strings
       let wc = count_words f2
       let wc10 = take 10 wc -- take only the first ten elements
       putStrLn ( show wc10 ) -- and print them