The "Do While False" idiom
Python 3, 31
Saved 1 byte thanks to xnor.
Only one byte away from ES6. :/ Stupid Python and its long anonymous function syntax.
Hooray for one liners!
lambda x,y:x*&quot;AB&quot;or&quot;AC&quot;+&quot;ED&quot;[y]

Test cases:
assert f(1, 1) == &quot;AB&quot;
assert f(1, 0) == &quot;AB&quot;
assert f(0, 1) == &quot;ACD&quot;
assert f(0, 0) == &quot;ACE&quot;