The duck programming language supports first-class functions, integer and floating-point arithmetic, string manipulation, dynamically-sized arrays, dictionary types, and basic object oriented programming. The syntax is strongly reminiscent of BASIC, Lua, or Python. While indentation is not strictly specified, the language requires specific whitespace in required newlines at the end of certain statements. Duck is currently only implemented in the form of a slow, interpreted frontend, making it useful as a portable scripting language. This frontend has been developed entirely in C.
function display_primes(limit) count = 0 numbers =  for i = 2 to limit do numbers[i] = 1 loop for i = 2 to limit do if numbers[i] == 1 then count = count + 1 for j = 2 to limit/i do numbers[i*j] = 0 loop duck.print(i) end loop end