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Re^2: Circular buffer

by mellon85 (Monk)
on Mar 20, 2011 at 17:11 UTC ( #894360=note: print w/replies, xml ) Need Help??

in reply to Re: Circular buffer
in thread Circular buffer

I don't like leaving the $pointer variable grow indefinitely.
This code is equivalent, but keeps $pointer in [0,@buffer). In fact, just gets the remainder after each $pointer change
my @buffer = (0) x 5; my $pointer = 0; for (0..30) { print "old value: ", $buffer[$pointer], "\n"; print "new value: $_\n"; $buffer[$pointer] = $_; $pointer = (++$pointer) % @buffer; }

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Re^3: Circular buffer
by moritz (Cardinal) on Mar 20, 2011 at 18:53 UTC

    I usually avoid code like $pointer = (++$pointer) % @buffer; where the same variable is modified twice within the same expression. It means that the outcome depends on the order of evaluation, which isn't defined in all cases (it is in the case of assignment though).

    Instead I'd just write $pointer = (1 + $pointer) % @buffer.

Re^3: Circular buffer
by repellent (Priest) on Mar 20, 2011 at 19:08 UTC
    No $pointer. @buffer always ordered last to most recent.
    my @buffer = (0) x 5; for (0..30) { print "old value: ", $buffer[0], "\n"; print "new value: $_\n"; shift @buffer; push @buffer, $_; }

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