gistfile1.rb

condition = false
puts "hello" if condition
#=> nil
# note there is no printing of `hello`, this means `conditions` was evaluated first before performing the preceding code
# this is expected and expanding the preceding code into `begin...end` yields you the same result

condition = false
begin
  puts "hello"
end if condition
#=> nil

# note there is no printing of `hello`, this means `condition` was evaluated first before trying to evaluate `begin..end`
#
#
#
#
# now let's try `while` instead of `if`

n = 3
(n -= 1).tap {|x| puts "# code: #{x}" } while n.tap {|x| puts "# condition: #{x}" } > 0
# condition: 3
# code: 2
# condition: 2
# code: 1
# condition: 1
# code: 0
# condition: 0
# => nil 

# note that condition was evaluated first (thus printed first). so this is consistent with the behavior of `code if condition` construct
#
# BUT if we expand code to `begin..end`

n = 3
begin
  (n -= 1).tap {|x| puts "# code: #{x}" }
end while n.tap {|x| puts "# condition: #{x}" } > 0
# code: 2
# condition: 2
# code: 1
# condition: 1
# code: 0
# condition: 0
 => nil 

# note that `begin...end` code is evaluated before `condition`.
# though this "looks like what other languages do", ruby is unfortunately inconsistent with itself.