Re: [Caml-list] infinity matches all

[Xavier Leroy <xavier.leroy@inria.fr>]

> Can anyone explain the following behavior of match when used with infinity?
> 
> # match "foo" with infinity -> "bar";;
> - : string = "bar"
> 
> This shouldn't even typecheck.  It seems to treat infinity as equivalent
> to "_".  This behavior comes up in version 3.06.

This is probably in the FAQ somewhere.  What confuses you is that this
occurrence of "infinity" is just a variable that is bound by the
matching; it's not a constructor, and it's not a constant.  Hence, you
code is equivalent (by renaming) to

        match "foo" with s -> "bar";;

and indeed to

        match "foo" with _ -> "bar";;

since _ behaves like a variable that isn't referenced in the r.h.s.

If you intend to match against the value of floating-point infinity, do

        match e with x when x = infinity -> ...

- Xavier Leroy

-------------------
To unsubscribe, mail caml-list-request@inria.fr Archives: http://caml.inria.fr
Bug reports: http://caml.inria.fr/bin/caml-bugs FAQ: http://caml.inria.fr/FAQ/
Beginner's list: http://groups.yahoo.com/group/ocaml_beginners