Damian Conway writes:
>
> There's no second iterator. Just C<for> walking through an array.
>
( questions in the form of answers :-)
so :
* "for" impose array context for first argument and doesnt care about
"nature" of the array which it was given eventually as an argument .
no multiple streams -- use parallel and friends.
* parallel and friends return lazy array ( for performance
considerations ???? ) _o_r_ "for" *notice* the parallel and ??? optimize
it away / dont know
for parallel(@a,@b) -> ($x,$y) { ... }
* every object with "next" method can function as iterator ???
_o_r_ we always have to inherit from "iterator" class .
what about reset/rewind ???
* $fh = open "myfile" ;
for <$fh> { ... while <$fh> { ... } ... }
both <$fh> *ultimately* use *the same* method call $fh.next , but
second <$fh> does it explicitely , while the first -- from under the
cloth of lazy array returned by $fh.each and "drived" by "for" .
* what does it mean that "for walks the array" ( keeping in mind that
that array may be usual or lazy and for have to not to care )
> >
> > What's the difference between a lazy array and an iterator? Is there
> > caching?
>
> Yes. A lazy array is a wrapper-plus-cache around an iterator.
>
$fh = open "file" ;
@a := $fh ;
print @a[3] # 4 calls to "$fh.next"
print @a[0] # no calls to "$fh.next"
is that the meaning of ...-plus-cache ????
>
> > Some of questions about iterators and stuff:
> >
> > 1- Are iterators now considered a fundamental type?
>
> Probably, since they're fundamental to I/O and C<for> loops.
>
>
so every class can define its own "next" method or inherit from
Iterator to be used as an iterator _o_r_ it ( class ) *always* have to
inherit from Iterator -- to be used as iterator ???
Naively , it seems that this is similar to booleans in perl -- no need to
inherit from special class to behave as boolean.
>
> > 2a- Is there an C<Iterator.toArray()> or C<.toList()> method?
>
> Iterator::each.
>
>
> > 2a1- The notion that Iterator.each() returns a lazy array seems a
> > little wierd. Isn't a lazy array just an iterator?
>
> No. It's an array that populates itself on-demand using an iterator.
>
what is the difference between the arrays @a, @b , ... here
????
$a = Iterator.new( ... )
@a = $a.each ;
@b := $a.each ;
@c := $a ;
@d is lazy = ( 1, 2, 3 ) ;
@f is lazy = $a.each ;
> Iterator: an object that returns successive values from some source
> (such as an array, a filehandle, or a coroutine)
isnt it *anything* having method "next" ???
why do I need a special type "iterator" ?
thanks ,
arcadi .
