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lumie1337/addName.hs

Created October 23, 2019 02:54
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addName.hs
addName counter names name = do
i <- readTVar counter
ns <- readTVar names
orElse addName' $ return ()
where
addName' = do
guard $ any ((== name) . snd) ns
writeTVar names ((i, name) : ns)
writeTVar counter (i + 1)
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