Ruby: True, False

true and false are builtin objects.

The following evaluates to false:

• false
• nil

Everything else is true (including 0, 0.0, "0", "", []). (this is similar to emacs lisp. 〔➤see Emacs Lisp Basics〕)

# -*- coding: utf-8 -*-
# ruby

if false then p "yes" else p "no" end # "no"

if nil then p "yes" else p "no" end   # "no"

if () then p "yes" else p "no" end # "no"
# Empty paren eval to nil, so false.

# -*- coding: utf-8 -*-
# ruby

if true then p "yes" else p "no" end # "yes"

if 0 then p "yes" else p "no" end    # "yes"

if 0.0 then p "yes" else p "no" end  # "yes"

if [] then p "yes" else p "no" end   # "yes"

if {} then p "yes" else p "no" end   # "yes"

if "" then p "yes" else p "no" end   # "yes"