Description
Questions:
1. (8 pt) Write FuncLang programs to process a list of strings. A string is a list of characters and each
character is represented using a number.
(a) (4 pt) Given you a list of strings, find a string that contains a given character. See the example
below.
$ (Find 88 (list (list 77 73) (list 89)))
$ ()
$ (Find 88 (list (list 77 73) (list 89) (list 88 90 76)))
$ (88 90 76)
(b) (4 pt) Given you a list of strings, return a string that concatenates all the strings in the list. See
the example below.
$ (Concatenate (list (list 1 2) (list 3 4) (list 5)))
$ (1 2 3 4 5)
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CS 342 Principles of Programming Languages Homework 5
2. (6 pt) Write a FuncLang program called Shuffle, which takes an input list, ”shuffles” it and returns a
list whose members are ordered randomly. You can use Random(lst) (it randomly selects an element
from the list) to write your program.
3. (20 pt) Extend the FuncLang interpreter by supporting ”>” and ”<” and ”=” on strings and lists,
supporting ”=” on boolean values. For ”=”, we return true if the two strings have the exact length and
content. Two list values are considered equal if they have the same size and each element of the list
is equal to corresponding element in the other list. For ”<” and ”>”, the string and list comparison
is done using the length of the strings and lists. That is, ”> first second” returns true if the first
string/list is longer than the second string/list; and ”< first second” returns true if the first string/list
is shorter than the second string/list.
For example,
$ (= ”abc” ”abc”)
#t
$ (= ”abc” ”abcdef”)
#f
$ (> ”abc” ”abcd”)
#f
$ (< ”abc” ”abcdef”)
#t
$ (= #t #t)
#t
$ (= #t #f)
#f
$ (= (list) (list))
#t
$ (= (list 1 2 3 4) (list 1 2 3 4))
#t
$ (= (list 1 2 3 4) (list 1 2 3 4 5))
#f
$ (= (list 1 2 3 4 (list)) (list 1 2 3 4 (list)))
#t
$ (= (car (list 1 2 3)) 1)
#t
$ (= (car (list 1 2 3)) 2)
#f
$ (= (cdr (list 1 2 3)) 2)
#f
$ (= (cdr (list 1 2 3)) (list 2 3))
#t
$ (= (cdr (list 1 2 3)) (cdr (list 4 2 3)))
#t
$ (= (cons 0 (list 1 2)) (list 0 (list 1 2)))
#f
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CS 342 Principles of Programming Languages Homework 5
$ (= (cons 0 (list 1 2)) (list 0 1 2))
#t
$ (> (list 1 2) (list))
#t
$ (> (list) (list 1))
#f
$ (< (list 1 2) (cdr (list 2 3 4 5)))
#t
4. (20 pt) Rajan’s textbook Chapter 5, Exercise 5.9.5
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