added verbose mode to show workings

1 files changed, 19 insertions, 4 deletions

diff --git a/challenge-090/james-smith/perl/ch-2.pl b/challenge-090/james-smith/perl/ch-2.pl
index 618a88f999..a8227b59f2 100644
--- a/challenge-090/james-smith/perl/ch-2.pl
+++ b/challenge-090/james-smith/perl/ch-2.pl
@@ -8,23 +8,38 @@ use Test::More;
 
 ## This is ripe for bit operators - as it is about multiplying/diving by 2...
 ## and checking for the value of the "1s" bit....
+#
+# To execute as a quiet test - use `perl ch-2.pl`
+#
+# To show workings run `perl ch-2.pl 1`
 
+my $flag = @ARGV && $ARGV[0] eq '1' ? 1 : 0;
 foreach(1..10) {
-  my $x = int rand(40);
-  my $y = int rand(40);
-  is( eth_mult( $x , $y ), $x*$y );
+  my $x = 100 + int rand(400);
+  my $y = 100 + int rand(400);
+  is( eth_mult( $x , $y, $flag ), $x*$y );
 }
 
 done_testing();
 
 sub eth_mult {
-  my( $n, $m ) = @_;
+  my( $n, $m, $verbose ) = @_;
+  $verbose ||= 0;
+  my $calc = $n*$m;
   my $res = 0;
+  say q() if $verbose;
   while($n) {
+    printf "%7d x %7d | %7s\n", $n, $m, $n&1 ? $m : q(.) if $verbose;
+    # The meat - use binary and
     $res += $m if $n&1;
     $m<<=1;
     $n>>=1;
   }
+  if( $verbose ) {
+    say    q(------------------+--------);
+    printf "                  | %7d (%7d)\n", $res, $calc;
+    say q();
+  }
   return $res;
 }