optional definition

[Edward Kmett]

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.

-Edward

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'.
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