[Haskell-cafe] There is no null; Maybe/Option types

Ketil Malde ketil at malde.org
Sat Apr 23 14:27:58 CEST 2011

Evan Laforge <qdunkan at gmail.com> writes:

>> Most of the (non-IO) runtime errors I get using Haskell software is
>> due to head or fromJust, it's actually quite annoying. 

> Just singling this one out because I've heard it before.  I've never
> gotten a runtime error from these.  It seems quite easy to just not
> use these functions.

Unfortunately, it is quite easy to just use them, too :-)  Sometimes I
just *know* that this list will never be empty, or that that Maybe will
never be nothing - but often I'm wrong.

Maybe is in a sense easier, as 'Maybe a' and 'a' are different types,
while there isn't a similarly elegant type distinction between lists
that may be empty and lists with at least one element.  Maybe is really
quite brilliant.

If I haven't seen further, it is by standing in the footprints of giants

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