Merge pull request #6521 from drbaggy/master

Tidied up

3 files changed, 35 insertions, 15 deletions

diff --git a/challenge-175/james-smith/README.md b/challenge-175/james-smith/README.md
index b1aad3d2c1..56bf461373 100644
--- a/challenge-175/james-smith/README.md
+++ b/challenge-175/james-smith/README.md
@@ -26,11 +26,14 @@ my @L = (31,31,28,31,30,31,30,31,31,30,31,30,31);
 
 sub last_day_of_months {
   my $yr = shift;
-  $L[2] = (my $ly  = !( $yr%400 && ( ($yr%4) || !($yr%100) ) )) ? 29 : 28;
-  my $last = 31 - ( int(($yr%100)/4) - $ly + 2 * (int(3 - $yr/100)%4) + $yr%100 ) % 7;
-  map { ( ($last += 35 - $L[$_-1]) > $L[$_] ) && ($last-=7);
+                        ## Compute if leap year - set the length of feb accordingly.
+  $L[2] = (my $ly  = !($yr%400) ^ !($yr%100) ^ !($yr%4) ) ? 29 : 28;
+                        ## Compute the last Sunday in december of the previous year
+  my $last = 31 - ( int($yr%100/4) - $ly + 6 - 2*$yr/100%4 + $yr%100 ) % 7;
+                        ## Finally work out the last days of the following 2 months.
+  map { $last-=7 if $L[$_] < ($last += 35 - $L[$_-1]);
         sprintf '%04d-%02d-%02d', $yr, $_, $last
-      } 1..12;
+      } 1..12
 }
 ```
 ### Notes
@@ -92,7 +95,7 @@ We can rewrite this as a 1-liner using `List::Util`s product function.
 Now there is a second nasty trick here - which if you are used to javascript *self-executing closure*. The trick allows us here to
 use the result of the totient calculation and use it to calculate the `t(n) + S( t(n) )` calculation without a *temporary* variable.
 
-The code reduces to, watch out for the two difference `$_[]` and the `$_->[]`...:
+The code reduces to this, watch out for the two difference `$_[]` and the `$_->[]`...:
 
 ```perl
 sub st {
@@ -104,3 +107,5 @@ sub st {
                   );
 }
 ```
+
+The longer form is about 10-15% faster - due to the map and use of external method product...
diff --git a/challenge-175/james-smith/perl/ch-1.pl b/challenge-175/james-smith/perl/ch-1.pl
index 369e3ced03..b4ec450c98 100644
--- a/challenge-175/james-smith/perl/ch-1.pl
+++ b/challenge-175/james-smith/perl/ch-1.pl
@@ -13,19 +13,35 @@ my @L = (31,31,28,31,30,31,30,31,31,30,31,30,31);
 ## calendar ranges from 1582 to 2016. The UK didn't adopt the calendar into 1754,
 ## where in large parts of Europe is was adopted from 1582.
 
-foreach my $yr ( @ARGV ) {
-  say join ' ', last_day_of_months( $yr );
+say "LONG";
+foreach ( @ARGV ) {
+  say "  @{[last_day_of_months($_)]}";
 }
+say "COMPACT";
+foreach ( @ARGV ) {
+  say "  @{[last_day_of_months($_)]}";
+}
+say '';
 
 sub last_day_of_months {
   my $yr = shift;
                         ## Compute if leap year - set the length of feb accordingly.
-  $L[2] = (my $ly  = !( $yr%400 && ( ($yr%4) || !($yr%100) ) )) ? 29 : 28;
+  $L[2] = (my $ly  = !($yr%400) ^ !($yr%100) ^ !($yr%4) ) ? 29 : 28;
                         ## Compute the last Sunday in december of the previous year
-  my $last = 31 - ( int(($yr%100)/4) - $ly + 2 * (int(3 - $yr/100)%4) + $yr%100 ) % 7;
+  my $last = 31 - ( int($yr%100/4) - $ly + 6 - 2*$yr/100%4 + $yr%100 ) % 7;
                         ## Finally work out the last days of the following 2 months.
-  map { ( ($last += 35 - $L[$_-1]) > $L[$_] ) && ($last-=7);
+  map { $last-=7 if $L[$_] < ($last += 35 - $L[$_-1]);
         sprintf '%04d-%02d-%02d', $yr, $_, $last
-      } 1..12;
+      } 1..12
+}
+
+#        1         2         3         4         5
+#23456789#123456789#123456789#123456789#123456789#1
+sub l {
+  my$y=pop;
+  $L[2]=(my$f=!($y%400)^!($y%100)^!($y%4))?29:28;
+  my$l=31-(int($y%100/4)-$f+6-2*$y/100%4+$y%100)%7;
+  map{$l-=7if$L[$_]<($l+=35-$L[$_-1]);
+      sprintf'%04d-%02d-%02d',$y,$_,$l}1..12
 }
 
diff --git a/challenge-175/james-smith/perl/ch-2.pl b/challenge-175/james-smith/perl/ch-2.pl
index 946839b86b..10738e46ee 100644
--- a/challenge-175/james-smith/perl/ch-2.pl
+++ b/challenge-175/james-smith/perl/ch-2.pl
@@ -33,10 +33,9 @@ say sprintf 'Expanded  - %10.6f %10.6f', $t2-$t1, 100*($t2-$t1)/($t1-$t0);
 
 sub st {
   state @T = (0,0);
-  $T[ $_[0] ] //= sub{$_[0]+st($_[0])}->(
-                  product
-                    map { $_->[0]**($_->[1]-1) * ($_->[0]-1) }
-                    factor_exp $_[0]);
+  $T[ $_[0] ] //= sub{ $_[0]+st($_[0]) }->(
+    product map { $_->[0]**($_->[1]-1) * ($_->[0]-1) } factor_exp $_[0]
+  );
 }
 
 sub sum_totients {