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Sample LRU cache in Perl 6?
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# Turns out this doesn't work because OrderedHash | |
# is sorted, not ordered | |
class Cache::LRU { | |
use OrderedHash; | |
has %.cache = {} does OrderedHash; | |
has UInt $.max_size = 20; | |
method get($key) { | |
return %.cache{$key}; | |
} | |
method set($pair) { | |
if $.cache{$pair.key}:exists { | |
# delete it to make sure that it gets | |
# added as most-recently used | |
$.cache{$pair.key}:delete; | |
} | |
elsif %.cache.pairs.elems >= $.max_size { | |
# key doesn't exist, so make room for it | |
%.cache{ %.cache.keys.tail }:delete; | |
} | |
%.cache{$pair.key} = $pair.value; | |
} | |
method pairs() { | |
return %.cache.pairs; | |
} | |
} | |
my $cache = Cache::LRU.new( max_size => 3 ); | |
for (1, 2, 3, 4, 5, 4, 3, 2).kv -> $i, $num { | |
say "# Setting $num to $i"; | |
$cache.set( $num => $i ); | |
# by the time we get to herre, 2, 3, and 4 are our last items, but I'm | |
# getting ("5" => 4, "1" => 0, "2" => 7).Seq | |
say "# " ~ $cache.pairs.perl; | |
} | |
# Setting 1 to 0 | |
# ("1" => 0,).Seq | |
# Setting 2 to 1 | |
# ("1" => 0, "2" => 1).Seq | |
# Setting 3 to 2 | |
# ("1" => 0, "3" => 2, "2" => 1).Seq | |
# Setting 4 to 3 | |
# ("1" => 0, "4" => 3, "3" => 2).Seq | |
# Setting 5 to 4 | |
# ("5" => 4, "1" => 0, "4" => 3).Seq | |
# Setting 4 to 5 | |
# ("5" => 4, "1" => 0, "4" => 5).Seq | |
# Setting 3 to 6 | |
# ("5" => 4, "1" => 0, "3" => 6).Seq | |
# Setting 2 to 7 | |
# ("5" => 4, "1" => 0, "2" => 7).Seq |
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