link repetit
February 25, 2003; Ralph E. Griswold
This file is in the public domain.
This procedure returns the length of the smallest range of values
that repeat in a list. For example, if
L := [1, 2, 3, 1, 2, 3, 1, 2, 3]
repetit(L) returns 3. If there is no repetition, repetit() returns
the length of the list.