\BV

\BV is a small domain-specific language with limited power defined in the task of the ICFP programming contest 2013.

A \BV program takes a single 64-bit integer as its input and returns a single 64-bit integer as the result. \BV is definitely not Turing complete: it only has one loop construct, fold, which does exactly 8 iterations of its body and is allowed only once per program.