<p>How can I list all the types that are declared by a module in Ruby?</p>

Use the
constants
method defined in the
Module
module. From the Ruby documentation:
Module.constants => array
Returns an array of the names of all
  constants defined in the system. This
  list includes the names of all modules
  and classes.
p Module.constants.sort[1..5]
produces:
["ARGV", "ArgumentError", "Array",
  "Bignum", "Binding"]
You can call
constants
on any module or class you would like.
```
```
p Class.constants
```
```