chapter 5

main.rb

@@ -2,6 +2,7 @@
 
 require './rlox/prompt'
 require './rlox/file'
+require './rlox/expression'
 
 case ARGV.length
   when 0 then prompt

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