Re: [Caml-list] Some/None

[Oliver Bandel <oliver@first.in-berlin.de>]

Ok,

I try an explanation, and you can comment it.


On Wed, 24 Apr 2002, Oliver Bandel wrote:
[...]
> How are Some/None defined, what are they good for?

To have a boolean choice and depending on that
choice giving back a value of arbitrary type
(or of type option).

> 
> A small, simple example will help a lot.

Hmhhh. I looked again into the answer of John Prevost
(my question on Stack overflow in try-statement)
and I'm close to understanding it.


[...]
> Can you explain me this type?

Hmhh, weell,  errr,, hmmhhh...

The type option gives two choices:
None or Some (== everything (?)).

A condition does not match => None
A condition does match => Some of arbritary type.

The Some/None-identifiers (constructors)
can be used for my is_regularfile-problem
too, I think.

But I have to think about it in more detail.
Does it make sense to give back None/Some
out of a function (e.g. is_regularfile/is_directory/...)
or is it only useful inside functions in
try- and match-statements?


Any correction of the above and any other explanations
are welcome...

Ciao,
   Oliver

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