in reply to Re^3: Constant value in anonymous sub (closures & aliases)
in thread Constant value in anonymous sub

> Rolf, $i is a variable and it is always mutable.

Doug, plz have a second look at the code (incl. errormsg) at the end of the post ... 8)

Cheers Rolf

UPDATE: Maybe it wasn't clearly enough expressed ...

for my $i ( LIST ) produces _aliases_ to the listelements (even to read-only values)!

It's NOT trivial (I would even say dangerous) when the explanation of closures has this extra complication, so it shouldn't be in any book.

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Re^5: Constant value in anonymous sub (closures & aliases)
by doug (Pilgrim) on Feb 23, 2010 at 14:27 UTC

    My point was simply that it was a good by the book example of a closure. I stand by that statement.

    Your issue seems to be more with how foreach makes its iterator variable an alias to the underlying object. I take it that you think it should be a copy, and not an alias? Well, that isn't very perl4-ish, and foreach has a long history. Just sticking with modern stuff, consider 

    foreach my $i ( @list ) {
   $i =~ s/foo/bar/g;
}
go_do_something(@list);

    [download]

    Would you expect the go_do_something() routine to get the unmodified values of @list, or would you expect the s/foo/bar/g transformation to have occured?

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