Reformatted for readability
Make RaiseError private
rename RaiseError
replace semicolons with newlines for readability
Prefer attr_accessor in favor of instance variables
Renamed stack to something more sensible
Use explicit initializer
clean up pop()

* unless with else makes our eyes bleed
* pop_the_Stack is not a rubyesque name
Clean up #pop

* Explicitly delegate to #list_of_stack_elements
* Remove unnecessary variable aliasing, creation of new array
* Why does this return 42? Nobody seems to care (see tests)
Remove unnecessary private methods

* pop_the_stack replaced by explicit delegation to list_of_stack_elements
* lessOne wasn't even used by anything
Clean up raise_error

* use a return guard to clean up logic
* move the puts before the raise, so it can actually do something
If you're going to have a raise_error, use it

* #top was just calling #raise