Is Dog|undef a legal type?
If we have a method that returns Dog if it returns anything at all, can we
say:
method foo returns Dog|undef {...}
In a similar vein, if the function reurns a dog or a refernce to an array
, can we use Dog|Array?
And is this legal:
given ($obj){
when Dog: ...
when Array: ...
#obviously $obj can be a ref to an array, not itself an array
}
--Abhijit
Abhijit A. Mahabal http://www.cs.indiana.edu/~amahabal/
Re: Is Dog|undef a legal type?
On Mon, Apr 19, 2004 at 11:00:33AM -0500, Abhijit A. Mahabal wrote:
: If we have a method that returns Dog if it returns anything at all, can we
: say:
:
: method foo returns Dog|undef {...}
Yes, but... You'd say that only if you wanted to allow a return
type that can be simultaneously Dog and undef, as well as either.
Remember that | is inclusive-OR, not exclusive. The default meaning of
method foo returns Dog {...}
is actually
method foo returns Dog^undef {...}
since any Object is implicitly allowed to be undef instead.
: In a similar vein, if the function reurns a dog or a refernce to an array
: , can we use Dog|Array?
Certainly. Again, you might wish to be more specific with Dog^Array,
though Dog|Array will certainly work, and is arguably more readable.
: And is this legal:
:
: given ($obj){
: when Dog: ...
: when Array: ...
: #obviously $obj can be a ref to an array, not itself an array
: }
Yes. Note that there's little distinction in Perl 6 between a ref to an
an array and the array itself. If you use an array in scalar context, you
automatically get the reference.
Larry
Re: Is Dog|undef a legal type?
Abhijit A. Mahabal skribis 2004-04-19 11:00 (-0500):
when Dog: ...
when Array: ...
Shouldn't that be:
when Dog { ... }
when Array { ... }
Or is there some .when that I have not yet heard of?
Juerd
Re: Is Dog|undef a legal type?
Abhijit A. Mahabal skribis 2004-04-19 11:00 (-0500):
when Dog: ...
when Array: ...
Shouldn't that be:
when Dog { ... }
when Array { ... }
Or is there some .when that I have not yet heard of?
Guilty as charged. My Perl6 is getting rusty...
--Abhijit
Re: Is Dog|undef a legal type?
On Mon, Apr 19, 2004 at 07:01:34PM +0200, Juerd wrote:
: Abhijit A. Mahabal skribis 2004-04-19 11:00 (-0500):
: when Dog: ...
: when Array: ...
:
: Shouldn't that be:
:
: when Dog { ... }
: when Array { ... }
Yes, that's how it should be written.
: Or is there some .when that I have not yet heard of?
Nope. I was just reading the previous as pseudocode, so I didn't say
anything about it.
Larry
