def undulate_up_down(l, repetitions = 1):
'''Wavelike motion up then down.
1. all elements, including greatest, ascending
2. all elements, excluding greatest, descending
Elements do not repeat at peaks and troughs.
'''
assert sequencetools.is_unique(l) and sequencetools.is_numeric(l)
ascending = list(sorted(l))
descending = list(sorted(reversed(l)))
descending = descending[1:-1]
period = ascending + descending
least = [min(l)]
result = period * repetitions + least
return result
def undulate_down_up(l, repetitions = 1):
'''Wavelike motion down then up.
1. all elements, including least, descending
2. all elements, excluding least, ascending
Maximum and minimum elements are not repeated at peaks and troughs.
'''
assert sequencetools.is_unique(l) and sequencetools.is_numeric(l)
descending = list(sorted(reversed(l)))
ascending = list(sorted(l))
ascending = ascending[1:-1]
period = descending + ascending
greatest = [max(l)]
result = period * repetitions + greatest
return result