Here’s an double tanka on Euclid’s algorithm (for finding the greatest common divisor of two numbers), executable as a Scheme program. My notes indicate that I wrote it during a tedious teleconference.
(define gcd (lambda (m n) (if (zero? n) m (gcd n (remainder m n))))) ; Look! ; Falling leaves unveil the tree. ; Two integers stand. ; They divide, m's ghost remains. ; As autumn passes, ; n succeeds m, floating down. ; Zero reveals the great truth.