From c002719d2390f78cb09bdd12de44e9f72a515bed Mon Sep 17 00:00:00 2001
From: James Moriarty <james.moriarty@rea-group.com>
Date: Thu, 22 Sep 2016 20:47:04 +1000
Subject: [PATCH] feature: quote.

---
 lib/lisp.rb       | 3 +++
 test/test_lisp.rb | 5 +++++
 2 files changed, 8 insertions(+)

diff --git a/lib/lisp.rb b/lib/lisp.rb
index 31e4c05..ca3a472 100644
--- a/lib/lisp.rb
+++ b/lib/lisp.rb
@@ -53,6 +53,9 @@ def self.execute expression, scope = global
       _, test, consequent, alternative = expression
       expression                       = if execute test, scope then consequent else alternative end
       execute expression, scope
+    when :quote
+      _, expression = expression
+      expression
     when :set!
       _, var, expression                     = expression
       if scope.has_key?(var) then scope[var] = execute expression, scope else raise "#{var} is undefined" end
diff --git a/test/test_lisp.rb b/test/test_lisp.rb
index dd7fba1..a6e45ff 100755
--- a/test/test_lisp.rb
+++ b/test/test_lisp.rb
@@ -52,6 +52,11 @@ def test_set!
     assert_raises(RuntimeError) { Lisp.eval("(set! foo 0)") }
   end
 
+  def test_quote
+    assert_equal [1,2,3], Lisp.eval("(quote (1 2 3))")
+    assert_equal [0,1,2,3], Lisp.eval("(+ (quote (0)) (quote (1 2 3)))")
+  end
+
   def test_begin
     assert_equal 4, Lisp.eval("(begin (define x 1) (set! x (+ x 1)) (* x 2))")
   end