Re: Getting for() to accept a tied array in one statement

Is it an absolute requirement to have all the code within the while/for expression? I.e. is the following acceptable:

my $iter = TQDM::tqdm(1..10);

while (<$iter>) {
    print "got [$_]\n";
}
[download]

If so, then the behaviour you want is easily achieved using overloaded '<>'.

Otherwise, I think you need a custom iterator function, e.g.

sub iterate ($&) {
    my ($ary, $code) = @_;
    for (@$ary) {
        print "progress bar: $_\n";
        $code->();
    }
}

sub tqdm { bless [ @_ ] }

iterate tqdm(1..10), sub {
    print "got [$_]\n";
};
[download]

Dave.

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Re^2: Getting for() to accept a tied array in one statement by perlancar (Hermit) on Apr 16, 2019 at 14:22 UTC
Yes, in this case the goal is on how easy it is to add a progress indicator to an existing code that uses for(). If a user has to change her for() to while(), that would count as less easy. It's akin in spirit to data dumping modules like XXX or Data::Dmp that returns its original argument so you can insert XXX or dmp just about anywhere in an existing Perl code. Next step after I conquer for(), will probably move on to while(). :-) Yes, I'll be looking into overloading the diamond operator or tying filehandle.	[reply]
Re^3: Getting for() to accept a tied array in one statement by dave_the_m (Monsignor) on Apr 16, 2019 at 15:01 UTC
I don't think its possible in perl to write a function foo() that will allow any of the following in the way you want: `for (foo(list)) { ... } while (foo(list)) { .... } while (<foo(list)>) { .... }` [download] assuming that for and while are the perl built-ins, and that you're not using source filtering or keyword plugins etc. Dave.	[reply] [d/l]