Sigma.fold

use Core

fun main () =
  let input =
    when
    | Array.length Sys.argv == 2 -> open_in Sys.argv.(1)
    | Array.length Sys.argv == 1 -> stdin
    | otherwise -> fail "usage: sigma [file]"
    end
  let result =
    In_channel.fold_lines input
      init: 0.0 f: do acc x ->
        acc + if (is_empty x) then 0.0 else x::Float
      end
  in
    print (Float.to_string result)