end abbreviates sexps with nil

1 files changed, 6 insertions, 7 deletions

diff --git a/lib/sexp/parse.rb b/lib/sexp/parse.rb
index adfd513..44052c2 100644
--- a/lib/sexp/parse.rb
+++ b/lib/sexp/parse.rb
@@ -34,6 +34,10 @@ class SExp
     @data = data
   end
 
+  def nil?
+    car.nil? && cdr.nil?
+  end
+
   def to_s
     if car.nil?
       "()"
@@ -75,13 +79,8 @@ def num_members(tokens)
 end
 
 def members_to_tree(members)
-  case members.length
-  when 0
-    nil
-  when 1
-    SExp.new(members[0], SExp.new)
-  when 2
-    SExp.new(members[0], members[1])
+  if members.empty?
+    SExp.new
   else
     SExp.new(members[0], members_to_tree(members[1..-1]))
   end