A ubiquitous programming pattern is to compute elements and store them in a list:
L = []
for k in range(n):
# call various functions here
# that compute "result"
L.append(result)
This approach has a number of disadvantages:
- The number of iterations is decided in advance. If there is a break instruction, then the preceding code takes care of both generating values and deciding when to stop. This is not desirable and lacks flexibility.
- It makes the assumption that the user wants the whole history of the computation, for all the iterations. Suppose we are only interested in the sum of all the computed values. If there are many computed values, it does not make sense to store them, as it is much more efficient to add them one at a time.