Bachelor of Arts and Science (B.A.S. or B.A.&Sc.) is an undergraduatebachelor's degree given by a small number of American universities and a fair number of universities in other English-speaking countries (including Canada and Australia). Generally, to receive a B.A.S. degree, a student would need to complete the general requirements for a bachelor degree and also the requirements for two different academic majors (or academic minors) -- one that usually leads to a B.A. degree and one that usually leads to a B.S. degree. The degree is meant to be a four-year degree, but many students will take five years to complete the program.
Technically speaking, it is not an example of a double degree, as universities only confer a single degree. "A single degree is granted to students who graduate with multiple majors."