FossilOrigin-Name: f181ea92bf9d0adda566afb9f62c7ef4fa313761377cd3cf888c83a0b14f5188

diff --git a/ruby/lib/lox/environment.rb b/ruby/lib/lox/environment.rb
new file mode 100644
index 0000000..3f32be2
--- /dev/null
+++ b/ruby/lib/lox/environment.rb
@@ -0,0 +1,17 @@
+module Lox
+  class Environment
+    def initialize
+      @values = {}
+    end
+
+    def define(name, value)
+      @values[name] = value
+    end
+
+    def get(token)
+      name = token.lexeme
+
+      @values.fetch(name) { raise RuntimeError.new(token, "Undefined variable '#{name}'.") }
+    end
+  end
+end
diff --git a/ruby/test/lox/test_environment.rb b/ruby/test/lox/test_environment.rb
new file mode 100644
index 0000000..8079a17
--- /dev/null
+++ b/ruby/test/lox/test_environment.rb
@@ -0,0 +1,23 @@
+require_relative "../test_helper"
+
+require "lox/environment"
+require "lox/error"
+require "lox/token"
+
+class TestEnvironment < Lox::Test
+  def setup
+    @env = Lox::Environment.new
+  end
+
+  def test_define
+    @env.define("name", "value")
+
+    assert_equal "value", @env.get(Lox::Token.new(:IDENTIFIER, "name", "name", 0))
+  end
+
+  def test_get
+    assert_raises Lox::RuntimeError, "Undefined variable name 'name'." do
+      @env.get(Lox::Token.new(:IDENTIFIER, "name", "name", 0))
+    end
+  end
+end