binarytrees.perl-1.perl added

using lexicals instead of array accesses

bench/binarytrees/binarytrees.perl-1.perl

@@ -0,0 +1,48 @@
+# The Computer Language Benchmarks Game
+# http://shootout.alioth.debian.org/
+#
+# contributed by Emanuele Zeppieri
+# modified by Reini Urban
+
+use integer;
+
+sub bottomup_tree { # item, depth
+    my $item = shift;
+    my $depth = shift;
+    return $item unless $depth;
+    my $value = $item * 2;
+    [ $item, bottomup_tree($value-1, $depth-1), bottomup_tree($value, $depth-1) ]
+}
+
+sub item_check {
+    my ($value, $left, $right) = @{ $_[0] };
+    return !ref($left) ? $value : $value + item_check($left) - item_check($right);
+}
+
+my $max_depth = shift @ARGV;
+my $min_depth = 4;
+
+$max_depth = $min_depth + 2 if $min_depth + 2 > $max_depth;
+
+my $stretch_depth = $max_depth + 1;
+my $stretch_tree = bottomup_tree(0, $stretch_depth);
+print "stretch tree of depth $stretch_depth\t check: ",
+    item_check($stretch_tree), "\n";
+undef $stretch_tree;
+
+my $longlived_tree = bottomup_tree(0, $max_depth);
+
+for ( my $depth = $min_depth; $depth <= $max_depth; $depth += 2 ) {
+    my $iterations = 2 << $max_depth - $depth + $min_depth - 1;
+    my $check = 0;
+
+    foreach my $i (1..$iterations) {
+        $check += item_check( bottomup_tree($i, $depth) );
+        $check += item_check( bottomup_tree(-$i, $depth) )
+    }
+
+    print 2*$iterations, "\t trees of depth $depth\t check: ", $check, "\n"
+}
+
+print "long lived tree of depth $max_depth\t check: ",
+    item_check($longlived_tree), "\n"