CSE 341
Assignment 1: Scheme Warmup

Write and test these functions using the Dr. Scheme development environment:

1. a function that computes the absolute value of a number, i.e. takes one numerical parameter and returns its absolute value

   example usage:

   > (abs-val -2.1221)
   2.1221
   

2. a function that takes a list of numbers and returns a list of the squares of the numbers (again, in the same order)

   example usage:

   > (square-list-alt '(1 5.2 7 -3 0))
   (1 27.04 49 9 0)
   

3. a function that takes a list of numbers and a number k and returns a list containing only those list elements which are greater than or equal to k

   Ordering should be preserved, i.e. the numbers in the returned list should be in the same order as in the original list.

   example usage:

   > (filter-ge '(1 5 7 -3 8 3 -4 4) 4)
   (5 7 8 4)
   

   Hint: See Exercise 10.5 in the Sethi text.

4. a function that takes a unary predicate (as a function) and a list and returns a list containing only those list elements for which the predicate is true, i.e. a list filtered according to the predicate

   example usage:

   > (define (non-negative x) (>= x 0))
   > (filter non-negative '(-2 3 -1 1 4))
   (3 1 4)
   

   Hint: Note that this function is just a generalization of the function in the previous exercise.