Re: [Caml-list] Subtypes in Ocaml

[Mark Wotton hons2001 <mrak@cs.usyd.edu.au>]

On Wed, 25 Apr 2001, Chris Hecker wrote:

> 
> >Patternmatching seems to do it. if this isn't the right way to do it,
> >please, someone let me know before i do something stupid.
> 
> I'm not 100% sure what you're saying.  My first interpretation of your
> question leads me to say "this is what variants and pattern matching
> are all about".  Since a variant is a union type, it can be a Literal
> and just an expression and pattern matching will let you choose which
> to interpret it as.

Yes, that was it.

I had a suspicion it was a dumb question... i'm just not used to using
pattern-matching like that. It's working nicely now.

> My second interpretation is that you want to have a function typed to
> only take a subset of the variant type.  In this case, you can either
> use exceptions (the default pattern match one, or one raised with a |
> _ -> failwith "bad type" if you don't want the compiler warnings), 

Yes, I want this too.
Pattern matching seems to do it nicely. I was doing without it and
wondering why everything was so hard...

> or I think you can do something with polymorphic variants, but I must
> admit to being kind of confused by them.

I might wait until i'm a hardcore ocaml hacker, then.
Might be a while.

mrak


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