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yamadapc/Main.hs Secret

Created December 14, 2015 14:18
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Main.hs
#!/usr/bin/env stack
-- stack runghc --package async
import Control.Concurrent
import Control.Concurrent.Async
import System.IO
fazRequestsHTTP = do
putStrLn "[http] Fetching google.com"
threadDelay 1000
putStrLn "[http] Fetching google.com/something"
threadDelay 1000
-- Retorna o resultado
return "<html>...</html>"
-- Todo programa em Haskell tem uma função main
main = do
hSetBuffering stdout LineBuffering
-- Começamos nosso thread
promessaParaResposta <- async fazRequestsHTTP
-- Essa linha vai ser impressa imediatamente
putStrLn "Eu apareço antes do callback ser executado!"
-- Esperamos pelo valor da promessa
valor <- wait promessaParaResposta
putStrLn ("valor: " ++ valor)
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