Re: pattern matching with keyword function

I think the first pipe is optional.  I like to include it just because I
think it looks better that way.  But the first pipe is really optional.

So you could define a piecewise linear function like this:

*let** piecewise x **=* *match** x **with*

*|**0* *->* *0*

*|**x **when** x **<* *0* *->* *-**1*

*|**x **when** x **>* *0* *->* *1* *;;*


You don't have to write it that way.  You could also write it this way if
you eliminate the first pipe:


*let** piecewise x **=* *match** x **with*

*0* *->* *0*

*|**x **when** x **<* *0* *->* *-**1*

*|**x **when** x **>* *0* *->* *1* *;;*


The only problem with my function definition is that it generates Warning
Message #8 about a pattern matching that is not exhaustive.  But if you
look at the function, it really is exhaustive.  An int is either 0, less
than 0 or greater than 0.  That's it!  So I think the warning can be safely
ignored.


Best,


Douglas.



On Fri, Apr 8, 2016 at 3:50 AM, cedlemo [email protected] [ocaml_beginners] <
[email protected]> wrote:

>
>
> Hi,
>
> I have "stumbled" on this simple function
>
> let rec flatten = function
> [] -> []
> | l::r -> l @ flatten r
>
> At first glance I asked myself why they don't use the last remaining
> element of the list
> then I see that the line
> [] -> []
>
> doesn't have any "|" at the beginning.
>
> Could you explain we how does that works?
> And maybe could you give me one or more links for informations/examples
> on the patterns matching
> with the function keywords.
>
> Thanks
>
> cedlemo
> 
>