From 378e963f8876d4751eb375555d9cc90738ab633d Mon Sep 17 00:00:00 2001
From: drbaggy <js5@sanger.ac.uk>
Date: Tue, 23 Feb 2021 04:19:14 +0000
Subject: solution to 101!

---
 challenge-101/james-smith/perl/ch-1.pl | 41 ++++++++++++++++++++++++++++++++++
 challenge-101/james-smith/perl/ch-2.pl | 35 +++++++++++++++++++++++++++++
 2 files changed, 76 insertions(+)
 create mode 100644 challenge-101/james-smith/perl/ch-1.pl
 create mode 100644 challenge-101/james-smith/perl/ch-2.pl

(limited to 'challenge-101')

diff --git a/challenge-101/james-smith/perl/ch-1.pl b/challenge-101/james-smith/perl/ch-1.pl
new file mode 100644
index 0000000000..ac89a45459
--- /dev/null
+++ b/challenge-101/james-smith/perl/ch-1.pl
@@ -0,0 +1,41 @@
+#!/usr/local/bin/perl
+
+use strict;
+
+use warnings;
+use feature qw(say);
+use Test::More;
+
+print_spiral( 1 .. $_ ) foreach 1..30;
+
+sub print_spiral {
+  say join q( ), map { sprintf '%2d', $_ } @{$_} foreach @{pack_spiral(@_)};
+  say '';
+}
+
+sub pack_spiral {
+  my( $rows, @in ) = ( 1, @_ );
+
+  ## Get the value for columns & rows which have the smallest gap
+  ## but still multiply to size of array (we choose rows to be
+  ## no greater than columns as printing is neater - but for no
+  ## other reason...
+
+  $rows = @in%$_ ? $rows : $_ foreach 2 .. sqrt @in;
+
+  my ($cols,$r,$c,@out) = (@in/$rows,$rows-1,-1);
+
+  ## We start bottom left...
+  ## because we use pre-inc we actually start 1 to the left of it!
+  ## as we "jump" before depositing the entry of the array...
+
+  while( $rows && $cols ) {         ## Do we have anything else to do?
+    $out[$r][++$c] = shift @in foreach 1..$cols--; # >>
+    $out[--$r][$c] = shift @in foreach 1..--$rows; # ^^
+    last unless $rows && $cols;     ## Skip if we have finished here
+    $out[$r][--$c] = shift @in foreach 1..$cols--; # <<
+    $out[++$r][$c] = shift @in foreach 1..--$rows; # vv
+  }
+
+  return \@out;
+}
diff --git a/challenge-101/james-smith/perl/ch-2.pl b/challenge-101/james-smith/perl/ch-2.pl
new file mode 100644
index 0000000000..e68bdbbca8
--- /dev/null
+++ b/challenge-101/james-smith/perl/ch-2.pl
@@ -0,0 +1,35 @@
+#!/usr/local/bin/perl
+
+use strict;
+
+use warnings;
+use feature qw(say);
+use Test::More;
+
+is( winding_number(qw(0 1 1 0 2 2)), 0 );
+is( winding_number(qw(0 1 -1 1 0 -3)), 1 );
+is( winding_number(qw(0 1 2 0 -6 0)), 1 );
+
+done_testing();
+
+sub winding_number {
+  ## Winding number is a generic way of working out whether a point lies
+  ## within a polygon - as this is not difficult we can implement the
+  ## trick for our triangle...
+  ## We have to work with edges - each edge in the code is represented
+  ## by ($a,$b) -> ($x,$y)... We start from the edge which joins the
+  ## "last" node to the first and then we work our way around the circle
+  ## The winding number goes up or down depening on whether the edge
+  ## crosses the +ve axis (adding or subtracking 1 depending on the
+  ## direction) - this boils down to the algorithm below..
+
+  my @pts = @_;
+  my ($a,$b,$wn) = @pts[-2,-1],0;
+  while( my($x,$y) = splice @pts,0,2 ) {
+    $wn += $a<=0 ? $y>0  && $a*$y-$x*$b >  0 ?  1 : 0
+                 : $y<=0 && $a*$y-$x*$b <= 0 ? -1 : 0;
+    ($a,$b)=($x,$y);
+  }
+  return $wn?1:0;
+}
+
-- 
cgit 


From 6fce46c86da21aa2e28fa353bc1c85c89cb9ee1c Mon Sep 17 00:00:00 2001
From: drbaggy <js5@sanger.ac.uk>
Date: Tue, 23 Feb 2021 05:04:19 +0000
Subject: tidied up layout

---
 challenge-101/james-smith/perl/ch-1.pl | 24 +++++++++++++-----------
 1 file changed, 13 insertions(+), 11 deletions(-)

(limited to 'challenge-101')

diff --git a/challenge-101/james-smith/perl/ch-1.pl b/challenge-101/james-smith/perl/ch-1.pl
index ac89a45459..18434b2b69 100644
--- a/challenge-101/james-smith/perl/ch-1.pl
+++ b/challenge-101/james-smith/perl/ch-1.pl
@@ -9,32 +9,34 @@ use Test::More;
 print_spiral( 1 .. $_ ) foreach 1..30;
 
 sub print_spiral {
-  say join q( ), map { sprintf '%2d', $_ } @{$_} foreach @{pack_spiral(@_)};
+  say join q( ), map { sprintf '%2d', $_ } @{$_}
+    foreach @{pack_spiral(@_)};
   say '';
 }
 
 sub pack_spiral {
-  my( $rows, @in ) = ( 1, @_ );
+  my $rows = 1;
 
   ## Get the value for columns & rows which have the smallest gap
   ## but still multiply to size of array (we choose rows to be
   ## no greater than columns as printing is neater - but for no
   ## other reason...
 
-  $rows = @in%$_ ? $rows : $_ foreach 2 .. sqrt @in;
+  $rows = @_%$_ ? $rows : $_ foreach 2 .. sqrt @_;
 
-  my ($cols,$r,$c,@out) = (@in/$rows,$rows-1,-1);
+  my ($cols,$r,$c,@out) = (@_/$rows,$rows-1,-1);
 
   ## We start bottom left...
   ## because we use pre-inc we actually start 1 to the left of it!
   ## as we "jump" before depositing the entry of the array...
-
-  while( $rows && $cols ) {         ## Do we have anything else to do?
-    $out[$r][++$c] = shift @in foreach 1..$cols--; # >>
-    $out[--$r][$c] = shift @in foreach 1..--$rows; # ^^
-    last unless $rows && $cols;     ## Skip if we have finished here
-    $out[$r][--$c] = shift @in foreach 1..$cols--; # <<
-    $out[++$r][$c] = shift @in foreach 1..--$rows; # vv
+  ## Remember shift by default operates on @_;
+
+  while( @_ ) {                                      # do until empty
+    $out[ $r ][ ++$c ] = shift foreach 1 .. $cols--; # >>
+    $out[ --$r ][ $c ] = shift foreach 1 .. --$rows; # ^^
+    last unless @_;                                  # exit if empty
+    $out[ $r ][ --$c ] = shift foreach 1 .. $cols--; # <<
+    $out[ ++$r ][ $c ] = shift foreach 1 .. --$rows; # vv
   }
 
   return \@out;
-- 
cgit 


From aa52dd453a66122e8a51ebbbe27222f7c9d47667 Mon Sep 17 00:00:00 2001
From: drbaggy <js5@sanger.ac.uk>
Date: Tue, 23 Feb 2021 05:06:12 +0000
Subject: use @_ as easier

---
 challenge-101/james-smith/perl/ch-2.pl | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

(limited to 'challenge-101')

diff --git a/challenge-101/james-smith/perl/ch-2.pl b/challenge-101/james-smith/perl/ch-2.pl
index e68bdbbca8..e9fbf7ed2c 100644
--- a/challenge-101/james-smith/perl/ch-2.pl
+++ b/challenge-101/james-smith/perl/ch-2.pl
@@ -23,9 +23,9 @@ sub winding_number {
   ## crosses the +ve axis (adding or subtracking 1 depending on the
   ## direction) - this boils down to the algorithm below..
 
-  my @pts = @_;
-  my ($a,$b,$wn) = @pts[-2,-1],0;
-  while( my($x,$y) = splice @pts,0,2 ) {
+  my ( $a, $b, $wn ) = @_[ -2, -1 ], 0;
+
+  while( my($x,$y) = splice @_, 0, 2 ) {
     $wn += $a<=0 ? $y>0  && $a*$y-$x*$b >  0 ?  1 : 0
                  : $y<=0 && $a*$y-$x*$b <= 0 ? -1 : 0;
     ($a,$b)=($x,$y);
-- 
cgit 


From cc69036ae26a587aa9a79156029c90fe67f7069a Mon Sep 17 00:00:00 2001
From: drbaggy <js5@sanger.ac.uk>
Date: Tue, 23 Feb 2021 05:10:43 +0000
Subject: tidied up initialiser

---
 challenge-101/james-smith/perl/ch-1.pl | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

(limited to 'challenge-101')

diff --git a/challenge-101/james-smith/perl/ch-1.pl b/challenge-101/james-smith/perl/ch-1.pl
index 18434b2b69..b223880b14 100644
--- a/challenge-101/james-smith/perl/ch-1.pl
+++ b/challenge-101/james-smith/perl/ch-1.pl
@@ -15,16 +15,14 @@ sub print_spiral {
 }
 
 sub pack_spiral {
-  my $rows = 1;
 
   ## Get the value for columns & rows which have the smallest gap
   ## but still multiply to size of array (we choose rows to be
   ## no greater than columns as printing is neater - but for no
   ## other reason...
 
-  $rows = @_%$_ ? $rows : $_ foreach 2 .. sqrt @_;
-
-  my ($cols,$r,$c,@out) = (@_/$rows,$rows-1,-1);
+  my( $rows ) = reverse grep { ! (@_ % $_) } 1 .. sqrt @_;
+  my( $cols, $r, $c, @out ) = ( @_/$rows, $rows-1, -1 );
 
   ## We start bottom left...
   ## because we use pre-inc we actually start 1 to the left of it!
-- 
cgit 


From 7fac9125976bc8d07f4f3203ad300887120c55aa Mon Sep 17 00:00:00 2001
From: drbaggy <js5@sanger.ac.uk>
Date: Tue, 23 Feb 2021 05:46:17 +0000
Subject: tidied up last line

---
 challenge-101/james-smith/perl/ch-2.pl | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

(limited to 'challenge-101')

diff --git a/challenge-101/james-smith/perl/ch-2.pl b/challenge-101/james-smith/perl/ch-2.pl
index e9fbf7ed2c..f34c8f5ebb 100644
--- a/challenge-101/james-smith/perl/ch-2.pl
+++ b/challenge-101/james-smith/perl/ch-2.pl
@@ -30,6 +30,6 @@ sub winding_number {
                  : $y<=0 && $a*$y-$x*$b <= 0 ? -1 : 0;
     ($a,$b)=($x,$y);
   }
-  return $wn?1:0;
+  return $wn%2;
 }
 
-- 
cgit 


From e1028616f2f800ca00c27c0bc63c419f5f041cc8 Mon Sep 17 00:00:00 2001
From: drbaggy <js5@sanger.ac.uk>
Date: Tue, 23 Feb 2021 05:57:05 +0000
Subject: whitespace

---
 challenge-101/james-smith/perl/ch-1.pl | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

(limited to 'challenge-101')

diff --git a/challenge-101/james-smith/perl/ch-1.pl b/challenge-101/james-smith/perl/ch-1.pl
index b223880b14..c3b75a4ff6 100644
--- a/challenge-101/james-smith/perl/ch-1.pl
+++ b/challenge-101/james-smith/perl/ch-1.pl
@@ -21,7 +21,7 @@ sub pack_spiral {
   ## no greater than columns as printing is neater - but for no
   ## other reason...
 
-  my( $rows ) = reverse grep { ! (@_ % $_) } 1 .. sqrt @_;
+  my( $rows )               = reverse grep { ! (@_ % $_) } 1 .. sqrt @_;
   my( $cols, $r, $c, @out ) = ( @_/$rows, $rows-1, -1 );
 
   ## We start bottom left...
@@ -32,7 +32,7 @@ sub pack_spiral {
   while( @_ ) {                                      # do until empty
     $out[ $r ][ ++$c ] = shift foreach 1 .. $cols--; # >>
     $out[ --$r ][ $c ] = shift foreach 1 .. --$rows; # ^^
-    last unless @_;                                  # exit if empty
+    last                       unless  @_;           # exit if empty
     $out[ $r ][ --$c ] = shift foreach 1 .. $cols--; # <<
     $out[ ++$r ][ $c ] = shift foreach 1 .. --$rows; # vv
   }
-- 
cgit