x

2 files changed, 36 insertions, 1 deletions

diff --git a/challenge-158/james-smith/README.md b/challenge-158/james-smith/README.md
index 74a5faa077..e11f4ed587 100644
--- a/challenge-158/james-smith/README.md
+++ b/challenge-158/james-smith/README.md
@@ -49,6 +49,31 @@ sub additive_primes {
  * The *increment* block is called at the end of the loop and so stores the value of `$p` if it is an additive prime, then it increments the loop with the next prime.
  * Rather than doing a split and sum we use repeated dividing and summing, as it is more efficient around 20-30% more efficient. The increased performance is probably due to avoiding the "duality" of perl variables storing numbers as numbers/strings.
 
+## Extra code
+
+Rewritten with single line for ...
+```perl
+sub additive_primes_div {
+  my @res;
+  for(my$p=2; my$s=0,(my $q=$p)<=$N;(is_prime$s)&&(push@res,$p),$p=next_prime$p) {
+    do { $s += $q % 10 } while $q = int $q / 10;
+  }
+  @res;
+}
+```
+
+Alternative form with `for split`:
+
+```perl
+sub additive_primes_split {
+  my @res;
+  for( my $p = 2; my $s = 0, $p <= $N ; $p = next_prime $p ) {
+    $s+=$_ for split //, $p;
+    push @res, $p if is_prime $s;
+  }
+  @res;
+}
+```
 # Challenge 2 - First series buban primes
 
 ***Write a script to compute first series cuban primes <= 1000. (First series cuban primes have the form `((x+1)^3-x^3)/(x+1-x)` = `3x^2+3x+1`)***
diff --git a/challenge-158/james-smith/perl/ch-1.pl b/challenge-158/james-smith/perl/ch-1.pl
index 1473ccb3cb..dd43aa3bc6 100644
--- a/challenge-158/james-smith/perl/ch-1.pl
+++ b/challenge-158/james-smith/perl/ch-1.pl
@@ -6,16 +6,19 @@ use warnings;
 use feature qw(say);
 use Math::Prime::Util qw(next_prime is_prime);
 use Benchmark qw(cmpthese);
+use List::Util qw(sum0);
 
 my $N = shift || 100;
-my $I = 5e6/$N;
+my $I = 1e7/$N;
 $I = 100 if $I<100;
 say join ', ', additive_primes_div();
 say join ', ', additive_primes_div_expanded();
 say join ', ', additive_primes_split();
+say join ', ', additive_primes_split_sum0();
 
 cmpthese( $I, {
   'split'   => sub { additive_primes_split();        },
+  'sum0'    => sub { additive_primes_split_sum0();   },
   'div'     => sub { additive_primes_div();          },
   'div_exp' => sub { additive_primes_div_expanded(); },
 } );
@@ -49,4 +52,11 @@ sub additive_primes_split {
   }
   @res;
 }
+sub additive_primes_split_sum0 {
+  my @res;
+  for( my $p = 2; $p <= $N ; $p = next_prime $p ) {
+    push @res, $p if is_prime sum0 split //, $p;
+  }
+  @res;
+}