[Haskell-beginners] mayBe stuck

Brent Yorgey byorgey at seas.upenn.edu
Fri Aug 6 08:38:56 EDT 2010

On Fri, Aug 06, 2010 at 11:15:52AM +0100, Colin Paul Adams wrote:
> >>>>> "Brent" == Brent Yorgey <byorgey at seas.upenn.edu> 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:


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


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

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