10.4.1

ruby/lib/lox/interpreter.rb

@@ -1,8 +1,11 @@
 require_relative "environment"
+require_relative "function"
 
 module Lox
   class Interpreter
 
+    attr_reader :globals
+
     def initialize(env=Environment.new)
       @globals = env
       @env = @globals
@@ -46,6 +49,12 @@ module Lox
       nil
     end
 
+    def visit_function(stmt)
+      function = Function.new(stmt)
+      @env.define(stmt.name.lexeme, function)
+      nil
+    end
+
     def visit_if(stmt)
       if truthy?(evaluate(stmt.cond))
         evaluate(stmt.then)

ruby/lib/lox/stmt.rb

@@ -13,7 +13,7 @@ module Lox
     end
 
     stmt :Block, :stmts
-    stmt :Fun, :name, :params, :body
+    stmt :Function, :name, :params, :body
     stmt :Expr, :expr
     stmt :If, :cond, :then, :else
     stmt :Print, :expr

ruby/test/lox/test_interpreter.rb

@@ -224,6 +224,17 @@ class TestInterpreter < Lox::Test
     SRC
   end
 
+  def test_function
+    assert_interpreted <<~EXPECTED.chomp, <<~SRC
+      Hi, Dear Reader!
+    EXPECTED
+      fun sayHi(first, last) {
+        print "Hi, " + first + " " + last + "!";
+      }
+
+      sayHi("Dear", "Reader");
+    SRC
+  end
   private
 
   def assert_interpreted(expected, src)