Re: RFC 57 (v1) Subroutine prototypes and parameters

Piers Cawley <[email protected]> writes:

> Perl6 RFC Librarian <[email protected]> writes:
> > This has a dangerous and unpredictable side-effect which we would rather 
> > avoid.  So the third and preferred candidate is: 
> > 
> >     foo(x = 10, y = 20);
> > 
> > In Perl 5 this is a syntax error raising a 'Bareword "x" not
> > allowed...'  error message.  This is a Good Thing because it implies
> > there aren't (m)any existing scripts that are currently using this
> > construct.  
> 
> 
>     sub x : lvalue { $x }
>     sub y : lvalue { $y }
> 
>     foo(x = 10, y = 20);
> 
> However, I note that:
> 
>     foo(x:10, y:20) 
> 
> throws a syntax error, as does:
> 
>     foo($x:10, $y:20)
> 
> Hey! So does:
> 
>     foo($x := 10, $y := 20)
> 
> But that looks painful.
> 
> I also note that given  
> 
>      sub ($x, $y, $z) { #stuff
>      }
> 
> It might be nice if:
> 
>      $curried_foo = foo(x:10, y:20);
> 
> returned an appropriately curried function... But Damian's already
> doing curries elsewhere...

Oops, just realised, that won't fit in with the possibility of the
defaulted values elsewhere. Maybe we could have:

    $curried_foo = foo(x := 10, y := 20)

do the currying, with a plain old colon being a named parameter type call.