From f23168670146fb6810d3293d5539579fe261db4d Mon Sep 17 00:00:00 2001
From: Tim Morgan <tim@timmorgan.org>
Date: Mon, 27 Jul 2015 20:58:27 -0500
Subject: [PATCH] Add boolean? predicate

---
 lib/bool.scm          |  7 +++++++
 spec/lib/bool_spec.rb | 48 +++++++++++++++++++++++++++++++++++++++++++
 vm.rb                 |  1 +
 3 files changed, 56 insertions(+)
 create mode 100644 lib/bool.scm
 create mode 100644 spec/lib/bool_spec.rb

diff --git a/lib/bool.scm b/lib/bool.scm
new file mode 100644
index 0000000..6dc236c
--- /dev/null
+++ b/lib/bool.scm
@@ -0,0 +1,7 @@
+(define boolean?
+  (lambda (b)
+    (if (eq? b #t)
+        #t
+        (if (eq? b #f)
+            #t
+            #f))))
diff --git a/spec/lib/bool_spec.rb b/spec/lib/bool_spec.rb
new file mode 100644
index 0000000..6d30350
--- /dev/null
+++ b/spec/lib/bool_spec.rb
@@ -0,0 +1,48 @@
+require_relative '../spec_helper'
+require 'stringio'
+
+describe 'Library' do
+  let(:stdout) { StringIO.new }
+
+  let(:subject) { Program.new(code, stdout: stdout) }
+
+  before { subject.run }
+
+  describe 'boolean?' do
+    context 'given #t' do
+      let(:code) do
+        <<-END
+          (boolean? #t)
+        END
+      end
+
+      it 'returns #t' do
+        expect(subject.vm.pop_val).to eq(VM::BoolTrue.instance)
+      end
+    end
+
+    context 'given #f' do
+      let(:code) do
+        <<-END
+          (boolean? #f)
+        END
+      end
+
+      it 'returns #t' do
+        expect(subject.vm.pop_val).to eq(VM::BoolTrue.instance)
+      end
+    end
+
+    context 'given a list' do
+      let(:code) do
+        <<-END
+          (boolean? (list))
+        END
+      end
+
+      it 'returns #f' do
+        expect(subject.vm.pop_val).to eq(VM::BoolFalse.instance)
+      end
+    end
+  end
+end
diff --git a/vm.rb b/vm.rb
index 35b19e9..66ce6d3 100644
--- a/vm.rb
+++ b/vm.rb
@@ -396,6 +396,7 @@ class VM
   LIBRARIES = %w(
     list
     pair
+    bool
   )
 
   def lib_sexps(lib)
-- 
2.34.2