in reply to Re^3: Getting for() to accept a tied array in one statement
in thread Getting for() to accept a tied array in one statement

Ah sorry, I stand corrected. I was reading your code as: for( do { tie my @x, "MyClass", "first", "second"; @x } ) {

So indeed: for( @{ tie my @x, "MyClass", "first", "second"; \@x } ) {

will make for() iterate over a tied array. In fact, 

use strict;
use warnings;

package MyClass;
    use Tie::Array;
    our @ISA = ('Tie::Array');
        our @data;
    # mandatory methods
    sub TIEARRAY { my $class = shift; bless \@data, $class; @data = @_
+; return \@data }
    sub FETCH { print "FETCH: "; my ($self, $index ) = @_; return $dat
+a[$index] }
    sub FETCHSIZE { return scalar @data }

package main;

    sub wrapper {
        tie my @x, "MyClass", @_;
        \@x;
    }

for( @{wrapper("first", "second")} ) {
        print "In loop = ";
        print "$_\n";
}

[download]

also works. So it's quite close to what I want, yay. Any improvement is welcome :-)

Replies are listed 'Best First'.
Re^5: Getting for() to accept a tied array in one statement
by hdb (Monsignor) on Apr 16, 2019 at 14:18 UTC

    Try this: 

        sub wrapper : lvalue {
        tie my @x, "MyClass", @_;
        @x;
    }

for( wrapper("first", "second") ) {
        print "In loop = ";
        print "$_\n";
}

    [download]

    As I said initially I am not expert in this, so there might be undesired side effects...

    And FETCHSIZE is called once only...

[reply]
[d/l]

      hdb, you're my hero :-) My faith in Perl is restored again.

[reply]

        Why do you want to make something so simple so complicated and expensive? Use an iterator! 

        sub make_list_iterator {
   my @list = @_;
   return sub {
      return () if !@list;
      return shift(@list);
   };
}

my $iter = make_list_iter("some", "el", "ems");
while ( my ($item) = $iter->() ) {
   ...
}

        [download]

        As a bonus, one doesn't need to know the length of the list in advance with an iterator!

[reply]
[d/l]

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