Re: [Caml-list] octothorpes and backticks?

[Anthony Tavener <anthony.tavener@gmail.com>]

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Backticks are for Polymorphic Variants...

Documentation is in plain sight... and yet kind of hidden. :) Here's the
Polymorphic Variants section of the manual:
http://caml.inria.fr/pub/docs/manual-ocaml/lablexamples.html#sec46

And at the bottom of the "Advanced Use" subsection it introduces the
abbreviated syntax for matching.

The Polymorphic Variant chapter of Real World OCaml might be useful too,
though I couldn't see any reference to the abbreviated matching with #,
even in the subtyping topic in the Objects chapter.

On Fri, Jun 10, 2016 at 1:05 PM, Hendrik Boom <hendrik@topoi.pooq.com>
wrote:

> On Fri, Jun 10, 2016 at 06:25:57PM +0000, dario.teixeira@yahoo.com wrote:
> > Hi,
> >
> > > (b) Is there any way to do a run-time type-test on a value of a
> > > specific statically known supertype to test whether it is actually a
> > > value of a known specified subtype, and if so to proceed to use it as
> > > that subtype?
> >
> > I reckon the "#" syntax may be what you are looking for.
> > It works with polymorphic variants and objects (types
> > where row-polymorphism applies).  Small example:
> >
> > type foo = [ `A | `B | `C ]
> > type bar = [ `D | `E | `F ]
> > type foobar = [ foo | bar ]
> >
> > let f = function
> >   | #foo -> "Foo"
> >   | #bar -> "Bar"
>
> Haven't encountered the 3 syntax or the ` syntax.  Where is it
> docuumented, so I can start to understand?
>
> -- hendrik
>
> >
> > Hope this helps!
> > Best regards,
> >
> > Dario Teixeira
>
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