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1 files changed, 31 insertions, 0 deletions

diff --git a/ch-2.pl b/ch-2.pl
new file mode 100644
index 0000000000..420c20d172
--- /dev/null
+++ b/ch-2.pl
@@ -0,0 +1,31 @@
+#!/usr/bin/perl
+use strict;
+use Test::Simple tests => 2;
+use List::Util qw/max sum/;
+
+#reference: https://www.tutorialspoint.com/perl/bitwise_operators_example.htm
+
+
+sub f {  # compare two bit-strings by xor
+    my $hint = ($_[0] ^ $_[1]) ;
+    my $ans = sum (split //, sprintf("%b", $hint));
+    return $ans;  
+}
+
+# first parameter: number of terms; remaining: terms in the list
+sub conclude {
+    my ($N, @val) = @_; 
+    my $sum = 0;
+    for my $i (0..$N-2) {
+       for my $j ($i+1..$N-1) {
+          $sum += f($val[$i], $val[$j]); 
+       }
+    }
+    return $sum; 
+}
+
+
+ok (conclude(3,2,3,4) == 6), "bad";
+ok (conclude(2,1,3)==1), "too bad";
+
+