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Re: Choosing between multiple closures

by Eily (Parson)
on Jun 12, 2014 at 07:42 UTC ( #1089660=note: print w/replies, xml ) Need Help??

in reply to Choosing between multiple closures

When you write \&increment( @_ ) you take a reference to the output of the increment sub, which already is a reference. And then, you don't return the result, so your do_something sub returns the result of the for statement, which is not what you expect.

You can correct your code by replacing \&increment( @_ ) with return increment(@_) (the & isn't actually useful here).

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Re^2: Choosing between multiple closures
by oakb (Scribe) on Jun 12, 2014 at 08:00 UTC
    Thank you, Eily. I just made the change to my actual code, and VOILA! It works.

    It makes perfect sense, too. My problem lay in not understanding the need to return the return — I guess having so many returns is counterintuitive to me.

    UPDATE: In the groggy wee morning hours, I understated the number of returns involved... the fix is actually returning the returned return. Yup, that's three returns, folks. No wonder I couldn't get my brain around it before reading Eily's elucidating answer.

    Even though I thanked Mark Jason Dominus in my OP, it was actually Chap. 2 of his book that originally led me astray, since it shows coderefs everywhere an anonymous subroutine is too large to include right in a dispatch table:
    $dispatch_table = { CHDIR => \&change_dir, LOGFILE => \&open_log_file, VERBOSITY => \&set_verbosity, ... => ..., };
    (Higher-Order Perl, p. 44)

    Of course, Chap. 2 didn't contemplate returning iterators, which don't really make an appearance until Chap. 4, so this is not a condemnation of MJD or his excellent book — without which I wouldn't even be using iterators in the first place. No, the fault is completely mine for mixing concepts MJD didn't intend to combine at that point in the book. Mea culpa.

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