Simple random string generating lambda in Ruby with a small chance that the length of your string will be one less than you expect.

random_string.rb

random_string = -> length, radix=36 { rand(radix ** length).to_s(radix) }
 
# Random string of length 42, maybe 41.
random_string.call(42)
 
# Four random digits
random_string.call(4, 10)
 
# Four random hex digits
random_string.call(4, 16)