Implement zero?

tomstuart · Jun 2, 2014 · fc43cce · fc43cce
1 parent de0ced4
commit fc43cce
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diff --git a/lib/atom.rb b/lib/atom.rb
@@ -53,4 +53,8 @@ def sub1
       raise unless result.number?
     end
   end
+
+  def zero?
+    symbol == :'0' ? TRUE : FALSE
+  end
 end
diff --git a/lib/evaluator.rb b/lib/evaluator.rb
@@ -45,6 +45,7 @@ def apply(env, arguments)
     null?: Primitive.new(:null?),
     atom?: Primitive.new(:atom?),
     eq?: Primitive.new(:eq?),
+    zero?: Primitive.new(:zero?),
     add1: Primitive.new(:add1),
     sub1: Primitive.new(:sub1)
   }