catchup: revisit Eratosthenes's prime calculation. Compute the execution time of a code. Determine if a single number is prime. Read text from a file into a list of lines; into a list of lists of words; into a single list of words.
Lecture notes:
The sieve of Eratosthenes:
Is n prime?
Reading "grook.txt"
Given a list of words, return a sorted list of the unique words.
Given a list of words, count how often each word occurs. (Didn't work so well on Alice in Wonderland.)
Reading Alice in Wonderland, count word frequency.