Comp210 Lab 10: More abstract functions, Homework Q&A

Abstract functions, Homework Q&A

On the current and future homeworks and exam, you are expected to use abstract functions where applicable. We've previously discussed map, filter, foldr, and foldl. Those are entirely sufficient, but today we'll introduce andmap, ormap, and build-list:

     (andmap f (list x1 ... xn)) = (and (f x1) ... (f xn))
     (ormap  f (list x1 ... xn)) = (or  (f x1) ... (f xn))
     (build-list nat f)          = (list (f 0) ... (f (sub1 nat)))

To do: Using abstract functions and lambda, write the following functions. All should be very short (2-4 lines each). Many have multiple solutions, even just with the given abstract functions.

• The sum of all the positive numbers in a list of numbers.
• Given a list containing anything, determine whether all of the numbers in the list are even.
• Given a list of lists, return the list of all the elements, e.g.,

       (flatten-one-level (list (list x1 ... xn) ... (list y1 ... ym))) =
       (list x1 ... xn ... y1 ... ym)
       

• (countup m n) = (list m ... (+ m n -1)). Assume n is non-negative.
• (append list1 list2)
• (insert n a-lon) and (insertion-sort a-lon). (It might be helpful to remind yourself how these functions were written following the templates.)

Come to lab prepared with intelligent homework questions, i.e., something more than "How do you solve part X?".