From 2e65ab3d2c506385e04f9219755780dfe11bb69f Mon Sep 17 00:00:00 2001
From: Ian Jackson <ijackson@chiark.greenend.org.uk>
Date: Fri, 20 Oct 2017 19:47:57 +0100
Subject: [PATCH] poster-tube-lid-parametric: support reversed sections

---
 poster-tube-lid-parametric.pl | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/poster-tube-lid-parametric.pl b/poster-tube-lid-parametric.pl
index 64a6003..68a0ed3 100755
--- a/poster-tube-lid-parametric.pl
+++ b/poster-tube-lid-parametric.pl
@@ -128,17 +128,22 @@ sub point ($$$$) {
 }
 
 sub get_sections_ptvals {
-    my $last_name;
+    my $last_ptval;
     my @out;
     while (my $name = shift @_) {
 	if ($name eq '-') {
-	    push @out, [ $last_name, 1.0 ];
+	    push @out, $last_ptval;
 	} else {
 	    my $count = shift @_;
+	    my $neg = sub { $_[0] };
+	    if ($count < 0) {
+		$count = -$count;
+		$neg = sub { 1- $_[0] };
+	    }
 	    foreach (my $ix = 0; $ix < $count; $ix++) {
-		push @out, [ $name, $ix/$count ];
+		push @out, [ $name, $neg->($ix/$count) ];
 	    }
-	    $last_name = $name;
+	    $last_ptval = [ $name, $neg->(1.0) ];
 	}
     }
     return @out;
-- 
2.30.2