Re: [Haskell-beginners] mayBe stuck

6 Aug 2010

      On Fri, Aug 06, 2010 at 11:15:52AM +0100, Colin Paul Adams wrote:
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"Brent" == Brent Yorgey  writes:
>> Since Haskell allows programming with partial functions, you
    >> always have this burden at present.
Brent> Yes.  But that doesn't mean there isn't value in the
    Brent> discipline of avoiding them.  The burden of making sure you
    Brent> never use fromJust (or head, or ...) is much lighter than the
    Brent> burden of proving that every such use is safe.
The burden is knowing whether or not a function is partial. It's that or
... that is the problem. This isn't flagged anywhere.
That's a very good point.  But it's the sort of thing you pick up
pretty quickly, I think.  Here are some off the top of my head, for
beginners reading this who might not already know:

  fromJust
  head
  tail
  init
  last
  (!!)

For a fuller list, take a look at the 'safe' package on Hackage [1],
which also provides many different safe alternatives.

-Brent

[1] http://hackage.haskell.org/package/safe