From c48c006b0bfb0b786d203658b99ca3f13fd76b98 Mon Sep 17 00:00:00 2001
From: Maxim Likhachev <envrm@yandex.ru>
Date: Sat, 20 Jun 2020 16:41:00 +0300
Subject: [PATCH] 008/104: sleep

---
 src/sleep.hs | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)
 create mode 100644 src/sleep.hs

diff --git a/src/sleep.hs b/src/sleep.hs
new file mode 100644
index 0000000..fdd6d26
--- /dev/null
+++ b/src/sleep.hs
@@ -0,0 +1,23 @@
+{-# LANGUAGE NoImplicitPrelude #-}
+
+import Prelude            (Int, IO, Maybe (Just, Nothing), String,
+                           (.), (*), (++),
+                           compare, flip, mapM_, putStrLn)
+import Control.Concurrent (threadDelay)
+import Control.Monad      ((>>=), (>>))
+import Data.List          (sortBy)
+import System.Environment (getArgs)
+import System.Exit        (exitFailure)
+import Text.Read          (readMaybe)
+
+microseconds :: Int
+microseconds = 1000000
+
+sleep :: String -> IO ()
+sleep time = wait (readMaybe time)
+    where wait Nothing  = putStrLn ("sleep: invalid time interval ‘" ++ time ++ "’") >> exitFailure
+          wait (Just n) = threadDelay (n * microseconds)
+
+main :: IO ()
+main = getArgs >>= mapM_ sleep . sortBy (flip compare) -- sort args to handle non-integer values firstly
+