optional definition

Edward Kmett ekmett at gmail.com
Sun Sep 1 14:22:52 UTC 2019

It would also render the combinator useless for its normal purpose.

optional is used mostly to try to run a parser and to either succeed with
its  result (wrapped in a Just) or _failing that_ to just  return Nothing
and carry on.

For monads like parsec, the first parse is the one that gets returned, so
the definition isn't symmetric in behavior.


On Sun, Sep 1, 2019 at 2:28 AM Dannyu NDos <ndospark320 at gmail.com> wrote:

> The current 'one or none' definition breaks the order of elements.
> It is more Ord-friendly to define it as 'none or one'.
> _______________________________________________
> Libraries mailing list
> Libraries at haskell.org
> http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.haskell.org/pipermail/libraries/attachments/20190901/416b5ad8/attachment.html>

More information about the Libraries mailing list