Re^2: Circular buffer


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Re^2: Circular buffer

by mellon85 (Monk)

on Mar 20, 2011 at 17:11 UTC ( [id://894360]=note: print w/replies, xml )

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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 + $pointer) % @buffer`. Perl 6 - second systems done right	[reply] [d/l] [select]
Re^3: Circular buffer by repellent (Priest) on Mar 20, 2011 at 19:08 UTC
No `$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, $_; }` [download]	[reply] [d/l] [select]

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