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-- this is an interactive program to read in two numbers and print their sum.
module Main where
main = readChan stdin abort $ \userInput ->
let inputLines = lines userInput in
readInt "Enter first number: " inputLines $ \num1 inputLines1 ->
readInt "Enter second number: " inputLines1 $ \ num2 _ ->
appendChan stdout ("Their sum is: " ++ show (num1 + num2)) abort done
readInt :: String -> [String] -> (Integer -> [String] -> Dialogue) -> Dialogue
readInt prompt inputLines succ =
appendChan stdout prompt abort $
case inputLines of
(l1 : rest) -> case (reads l1) of
[(x,"")] -> succ x rest
_ -> appendChan stdout
"Error - retype the number\n" abort $
readInt prompt rest succ
_ -> appendChan stdout "Early EOF" abort done
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