From 1757aacde64adb5598a2b456035a1726269dbda5 Mon Sep 17 00:00:00 2001
From: Scott Steadman <ss@stdmn.com>
Date: Fri, 15 Aug 2014 11:10:01 -0700
Subject: [PATCH 1/4] Implemented quote.

  My knowledge of scheme is primitive. So I only created a simple test.
---
 README.md         | 2 +-
 lib/lisp.rb       | 3 +++
 test/test_lisp.rb | 5 +++++
 3 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/README.md b/README.md
index d234942..c034411 100644
--- a/README.md
+++ b/README.md
@@ -45,7 +45,7 @@ Features
 
 - [x] __conditional__ -	(if test conseq alt)	Evaluate test; if true, evaluate and return conseq; otherwise evaluate and return alt. _Example: (if (< 10 20) (+ 1 1) (+ 3 3)) ⇒ 2_
 
-- [ ] __quotation__	- (quote exp) Return the exp literally; do not evaluate it. _Example: (quote (a b c)) ⇒ (a b c)_
+- [x] __quotation__	- (quote exp) Return the exp literally; do not evaluate it. _Example: (quote (a b c)) ⇒ (a b c)_
 
 - [ ] __assignment__ -	(set! var exp)	Evaluate exp and assign that value to var, which must have been previously defined (with a define or as a parameter to an enclosing procedure). _Example: (set! x2 (* x x))_
 
diff --git a/lib/lisp.rb b/lib/lisp.rb
index b943d9e..fbc2cdf 100644
--- a/lib/lisp.rb
+++ b/lib/lisp.rb
@@ -52,6 +52,9 @@ def self.execute(exp, scope = global)
       _, test, conseq, alt = exp
       exp = execute(test, scope) ? conseq : alt
       execute(exp, scope)
+    when :quote
+      _, exp = exp
+      exp
     else
       func, *args = exp.map { |exp| execute(exp, scope) }
       func.call(*args)
diff --git a/test/test_lisp.rb b/test/test_lisp.rb
index c78141d..1f2bd45 100755
--- a/test/test_lisp.rb
+++ b/test/test_lisp.rb
@@ -54,4 +54,9 @@ def test_lambda
     Lisp.eval("(define fact (lambda (n) (if (<= n 1) 1 (* n (fact (- n 1))))))")
     assert_equal 3628800, Lisp.eval("(fact 10)")
   end
+
+  def test_quote
+    assert_equal [:a, :b, :c], Lisp.eval('(quote (a b c))')
+  end
+
 end

From 2447a4e95f3193ebd3810abb80611ece0948379c Mon Sep 17 00:00:00 2001
From: Scott Steadman <ss@stdmn.com>
Date: Fri, 15 Aug 2014 11:26:44 -0700
Subject: [PATCH 2/4] Implemented assignment.

---
 README.md         |  2 +-
 lib/lisp.rb       |  6 ++++++
 test/test_lisp.rb | 11 +++++++++++
 3 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/README.md b/README.md
index c034411..4f00e6e 100644
--- a/README.md
+++ b/README.md
@@ -47,6 +47,6 @@ Features
 
 - [x] __quotation__	- (quote exp) Return the exp literally; do not evaluate it. _Example: (quote (a b c)) ⇒ (a b c)_
 
-- [ ] __assignment__ -	(set! var exp)	Evaluate exp and assign that value to var, which must have been previously defined (with a define or as a parameter to an enclosing procedure). _Example: (set! x2 (* x x))_
+- [x] __assignment__ -	(set! var exp)	Evaluate exp and assign that value to var, which must have been previously defined (with a define or as a parameter to an enclosing procedure). _Example: (set! x2 (* x x))_
 
 - [ ] __sequencing__ -	(begin exp...)	 Evaluate each of the expressions in left-to-right order, and return the final value. _Example: (begin (set! x 1) (set! x (+ x 1)) (* x 2)) ⇒ 4_
diff --git a/lib/lisp.rb b/lib/lisp.rb
index fbc2cdf..0e8ea7f 100644
--- a/lib/lisp.rb
+++ b/lib/lisp.rb
@@ -55,6 +55,12 @@ def self.execute(exp, scope = global)
     when :quote
       _, exp = exp
       exp
+    when :set!
+      _, var, exp = exp
+      unless scope.has_key?(var)
+        raise "#{var} must be defined before you can set! it"
+      end
+      scope[var] = execute(exp, scope)
     else
       func, *args = exp.map { |exp| execute(exp, scope) }
       func.call(*args)
diff --git a/test/test_lisp.rb b/test/test_lisp.rb
index 1f2bd45..63a81e8 100755
--- a/test/test_lisp.rb
+++ b/test/test_lisp.rb
@@ -59,4 +59,15 @@ def test_quote
     assert_equal [:a, :b, :c], Lisp.eval('(quote (a b c))')
   end
 
+  def test_assignment
+    ex = assert_raises(RuntimeError) { Lisp.eval('(set! foo 42)') }
+    assert_equal 'foo must be defined before you can set! it', ex.message
+
+    Lisp.eval('(define foo 3.14)')
+    assert_equal 42, Lisp.eval('(set! foo 42)')
+    assert_equal 42, Lisp.eval('(* 1 foo)')
+
+    assert_equal -42, Lisp.eval('(set! foo (* -1 foo))')
+  end
+
 end

From d65de5e79412e26bac82d70797ca20ff1a3a2750 Mon Sep 17 00:00:00 2001
From: Scott Steadman <ss@stdmn.com>
Date: Fri, 15 Aug 2014 11:40:04 -0700
Subject: [PATCH 3/4] Implemented sequencing.

---
 README.md         | 2 +-
 lib/lisp.rb       | 3 +++
 test/test_lisp.rb | 4 ++++
 3 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/README.md b/README.md
index 4f00e6e..421b5f6 100644
--- a/README.md
+++ b/README.md
@@ -49,4 +49,4 @@ Features
 
 - [x] __assignment__ -	(set! var exp)	Evaluate exp and assign that value to var, which must have been previously defined (with a define or as a parameter to an enclosing procedure). _Example: (set! x2 (* x x))_
 
-- [ ] __sequencing__ -	(begin exp...)	 Evaluate each of the expressions in left-to-right order, and return the final value. _Example: (begin (set! x 1) (set! x (+ x 1)) (* x 2)) ⇒ 4_
+- [x] __sequencing__ -	(begin exp...)	 Evaluate each of the expressions in left-to-right order, and return the final value. _Example: (begin (define x 1) (set! x (+ x 1)) (* x 2)) ⇒ 4_
diff --git a/lib/lisp.rb b/lib/lisp.rb
index 0e8ea7f..f0a9321 100644
--- a/lib/lisp.rb
+++ b/lib/lisp.rb
@@ -61,6 +61,9 @@ def self.execute(exp, scope = global)
         raise "#{var} must be defined before you can set! it"
       end
       scope[var] = execute(exp, scope)
+    when :begin
+      _ = exp.shift
+      exp.map { |exp| execute(exp) }.last
     else
       func, *args = exp.map { |exp| execute(exp, scope) }
       func.call(*args)
diff --git a/test/test_lisp.rb b/test/test_lisp.rb
index 63a81e8..4142070 100755
--- a/test/test_lisp.rb
+++ b/test/test_lisp.rb
@@ -70,4 +70,8 @@ def test_assignment
     assert_equal -42, Lisp.eval('(set! foo (* -1 foo))')
   end
 
+  def test_sequencing
+    assert_equal 4, Lisp.eval('(begin (define x 1) (set! x (+ x 1)) (* x 2))')
+  end
+
 end

From 0852dc9e2f8288571b8b57f9e532523c829b0cb1 Mon Sep 17 00:00:00 2001
From: Scott Steadman <ss@stdmn.com>
Date: Wed, 20 Aug 2014 14:56:16 -0700
Subject: [PATCH 4/4] Added display keyword.

---
 README.md         | 2 ++
 lib/lisp.rb       | 7 ++++++-
 test/test_lisp.rb | 5 +++++
 3 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/README.md b/README.md
index 421b5f6..f88a839 100644
--- a/README.md
+++ b/README.md
@@ -50,3 +50,5 @@ Features
 - [x] __assignment__ -	(set! var exp)	Evaluate exp and assign that value to var, which must have been previously defined (with a define or as a parameter to an enclosing procedure). _Example: (set! x2 (* x x))_
 
 - [x] __sequencing__ -	(begin exp...)	 Evaluate each of the expressions in left-to-right order, and return the final value. _Example: (begin (define x 1) (set! x (+ x 1)) (* x 2)) ⇒ 4_
+
+- [x] __display__ -	(display exp...)	 Evaluate each of the expressions in left-to-right order, and write each result to STDOUT. _Example: (display Hello World! 42) ⇒ Hello World! 42_
diff --git a/lib/lisp.rb b/lib/lisp.rb
index f0a9321..fb61fed 100644
--- a/lib/lisp.rb
+++ b/lib/lisp.rb
@@ -30,8 +30,10 @@ def self.parse(tokens, tree = [])
 
   def self.evaluator(token)
     case token
-    when /\d/
+    when /\d*\.\d*/
       token.to_f
+    when /\d/
+      token.to_i
     else
       token.to_sym
     end
@@ -64,6 +66,9 @@ def self.execute(exp, scope = global)
     when :begin
       _ = exp.shift
       exp.map { |exp| execute(exp) }.last
+    when :display
+      _ = exp.shift
+      exp.map { |exp| execute(exp) || exp }.join(' ').tap { |str| puts str }
     else
       func, *args = exp.map { |exp| execute(exp, scope) }
       func.call(*args)
diff --git a/test/test_lisp.rb b/test/test_lisp.rb
index 4142070..ff82add 100755
--- a/test/test_lisp.rb
+++ b/test/test_lisp.rb
@@ -74,4 +74,9 @@ def test_sequencing
     assert_equal 4, Lisp.eval('(begin (define x 1) (set! x (+ x 1)) (* x 2))')
   end
 
+  def test_display
+    assert_output("Hello World! 42\n")  { Lisp.eval('(display Hello World! 42)') }
+    assert_output("Evaluated: 3.14\n") { Lisp.eval('(display Evaluated: (* 1 3.14))') }
+  end
+
 end