doing 7.2

cookbook/007/02.rb

@@ -0,0 +1,21 @@
+def call_twice
+  puts "I'm about to call your block."
+  yield
+  puts "I'm about to call your block again."
+  yield
+end
+
+call_twice { puts "Hi, I'm a talking code block." }
+
+
+def repeat(n)
+  if block_given?
+    n.times { yield }
+  else
+    raise ArgumentError.new("I can't repeat a block you don't give me!")
+  end
+end
+
+repeat(4) { puts "Hello." }
+
+repeat(4)