Chapter 3

1. The answer is exactly the one covered in the chapter:

   ​	​class​ Symbol
   ​	​def​ to_proc
   ​	proc { |obj, args| obj.send(self, *args) }
   ​	​end​
   ​	​end​

2. Since we’re interested in adding behavior to object initialization, it therefore makes sense to implement to_proc within the Class class. Here’s a possible implementation:

   ​	​class​ Class
   ​	​def​ to_proc
   ​	proc { |args| ​new​(*args) }
   ​	​end​
   ​	​end​

   Since we’re creating objects with arrays, each array element is treated as a single object. Therefore, the proc takes a single argument.

   Next, we use the splat operator to convert the array into method arguments, and pass it into new, which then calls the initializer.

3. The Proc#lambda? method.

4. Both come from the Proc class.

5. join_2. Lambdas are strict with arity.

6. Both. 1 + 2 + nil will raise an error.