Question

I’ve got the function:

isSortedUp x y z = if x>y && y>z then True else False

and I want to put it into module UP.

This function I want to put into module down:

isSortedDown x y z = if x<y && y<z then True else False

And then call them in the main program:

import System.Environment
import Up
import Down
main = do
  args<-getArgs
  let a = args !! 0
  let b = args !! 1
  let c = args !! 2
  if (isSortedUp a b c) || (isSortedDown a b c) then return (True) else return(False)

How to put and call this functions?

New code
Main.hs

import System.Environment
import Up
import Down  
main = do
  args<-getArgs
  let a = args !! 0
  let b = args !! 1
  let c = args !! 2
  if (isSortedUp a b c) || (isSortedDown a b c) then return(True) else return(False)

Up.hs

module Up (isSortedUp) where
isSortedUp x y z = if x>y && y>z then return(True) else return(False)

Down.hs

module Down (isSortedDown) where
isSortedDown x y z = if x<y && y<z then return(True) else return(False)

Answer 1

Modules in Haskell are broken up by file. So to put isSortedDown in it’s own module Down, you’d create a new file Down.hs and drop it’s contents inside with the module declaration:

module Down (isSortedDown) where

isSortedDown x y z = if x<y && y<z then True else False

Then, providing your Main module has access to this module (in the same directory, for instance), it should import and be accessible.

For more information on modules in Haskell, read:

• http://www.haskell.org/tutorial/modules.html
• http://learnyouahaskell.com/modules (Specifically the “Making your
  own modules” section — near the bottom)