This is a hack, since 'undefined' cannot be detected in general. The clean solution would be to find out where invalid file descriptors are detected in the IO code, and throw a real IOException instead of an 'error'.
On Fri, 11 Mar 2011, Daniel Peebles wrote:
Check out the spoon package on hackage. It's designed for these kinds of situations, and
will wrap up common user-generated "pure" exceptions into a Maybe (and will return
Nothing in the cases you describe)
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