From 6ac116c169cf2f0c795fd0fbc10424f7fafd70e7 Mon Sep 17 00:00:00 2001
From: hellerve <veit@veitheller.de>
Date: Tue, 24 Jul 2018 15:30:43 +0200
Subject: [PATCH] chapter 5

---
 main.rb            |  1 +
 rlox/expression.rb | 32 ++++++++++++++++++++++++++++++++
 2 files changed, 33 insertions(+)
 create mode 100644 rlox/expression.rb

diff --git a/main.rb b/main.rb
index b9d0042..6f07e66 100644
--- a/main.rb
+++ b/main.rb
@@ -2,6 +2,7 @@
 
 require './rlox/prompt'
 require './rlox/file'
+require './rlox/expression'
 
 case ARGV.length
   when 0 then prompt
diff --git a/rlox/expression.rb b/rlox/expression.rb
new file mode 100644
index 0000000..e05ac98
--- /dev/null
+++ b/rlox/expression.rb
@@ -0,0 +1,32 @@
+def parenthesize(name, *exprs)
+  res = "(#{name}"
+
+  exprs.each { | expr |
+    res << " "
+    res << expr.dbg
+  }
+  res << ")"
+
+  res
+end
+
+Binary = Struct.new(:left, :operator, :right) do
+  def dbg()
+    parenthesize(operator.lexeme, left, right)
+  end
+end
+Grouping = Struct.new(:expression) do
+  def dbg()
+    parenthesize("group", expression)
+  end
+end
+Literal = Struct.new(:value) do
+  def dbg()
+    value.to_s
+  end
+end
+Unary = Struct.new(:operator, :right) do
+  def dbg()
+    parenthesize(operator.lexeme, right)
+  end
+end