This means its an unboxed tuple. See recent thread about boxed vs. unboxed. -- Hal Daume III "Computer science is no more about computers | hdaume@isi.edu than astronomy is about telescopes." -Dijkstra | www.isi.edu/~hdaume On Fri, 4 Oct 2002, David Sabel wrote:

Hi,

can somebody explain what the notation (# ... #) means?

For example it is used in the definition of unsafePerformIO:

unsafePerformIO :: IO a -> a unsafePerformIO (IO m) = case m realWorld# of (# _, r #) -> r

Thanks, David

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