Sums numbers on the command line.

total.hs

#! /usr/bin/env stack
-- stack --resolver lts-8.15 --install-ghc script --package base

-- Usage:
--   $ echo -e "1.2 3.4\n5.6 not-a-number" | ./total.hs
--   10.2

import Data.Maybe (mapMaybe)
import Text.Read (readMaybe)

main :: IO ()
main =
  print
  . (\x -> x :: Double)
  . sum
  . mapMaybe readMaybe
  . words
  =<< getContents