8.3.1

FossilOrigin-Name: d3638720b7f16b1b5de8cec037b39a3bc9145f029a6456cb1772ddb3a852075f

ruby/lib/lox/interpreter.rb

@@ -1,5 +1,12 @@
+require_relative "environment"
+
 module Lox
   class Interpreter
+
+    def initialize
+      @env = Environment.new
+    end
+
     # The book does printing and error catching here, but
     # we're going to do it in the runner instead.
     def interpret(stmts)
@@ -20,6 +27,12 @@ module Lox
       nil
     end
 
+    def visit_var(stmt)
+      value = stmt.initializer&.yield_self { evaluate(_1) }
+      @env.define(stmt.name.lexeme, value)
+      nil
+    end
+
     def visit_grouping(expr) = evaluate(expr.expr)
     def visit_literal(expr)  = expr.value
 
@@ -35,6 +48,10 @@ module Lox
       end
     end
 
+    def visit_variable(expr)
+      @env.get(expr.name)
+    end
+
     def visit_binary(expr)
       left = evaluate(expr.left)
       right = evaluate(expr.right)

ruby/test/lox/test_interpreter.rb

@@ -97,6 +97,16 @@ class TestInterpreter < Lox::Test
     SRC
   end
 
+  def test_environment
+    assert_interpreted <<~EXPECTED.chomp, <<~SRC
+      3
+    EXPECTED
+      var a = 1;
+      var b = 2;
+      print a + b;
+    SRC
+  end
+
   private
 
   def assert_interpreted(expected, src)