Damian Conway writes:
> David Wheeler asked:
>
> > How will while behave?
>
> C<while> evaluates its first argument in scalar context, so:
>
>
> > while <$fh> {...} # Iterate until $fh.readline returns EOF?
>
> More or less. Technically: call <$fh.next> and execute the loop
> body if that method returns true. Whether it still has the
> automatic binding to $_ and the implicit definedness check is yet
> to be decided.
>
>
> > while <$iter> {...} # Iterate until $iter.each returns false?
>
> Yes.
>
you mean "Iterate until $iter.next returns false?"
what is the difference between the Iterator and lazy array ?
am I right that it is just "interface" : lazy array is an iterator
object "inside" Array interface : ????
Larry Wall wrote:
> Then there's this approach to auto-iteration:
>
> my @dance := Iterator.new(@squares);
> for @dance {
but then each is very simple method :
class Iterator {
method each( $self:) {
my @a := $self ;
return @a ;
}
}
but then probably we dont need two methods -- next and each .
just like in perl5 each can determine the calling context
class Iterator {
method each( $self:) {
when want Scalar {
...
}
when want Array {
my @a := $self ;
return @a ;
}
}
}
and then <...> could be *really* the sugar for .each ( or .next if it
will be called so ) . in these examples
> In a scalar context:
>
> <$fh> # Calls $fh.readline (or maybe that's $fh.next???>
> <$iter> # Calls $iter.next
> fibs() # Returns iterator object
> <fibs()> # Returns iterator object and calls that
> # object's C<next> method (see note below)
>
>
> In a list context:
>
> <$fh> # Calls $fh.each
> <$iter> # Calls $iter.each
> fibs() # Returns iterator object
> <fibs()> # Returns iterator object and calls object's C<each>
>
<...> *always* force call to .each ( which is context aware ) .
but again all that is based on the assumtion that lazy array is just
Iterator object in the "cloth" of array ( variable container ) . so
this is a question .
arcadi
