CIS 554 Clojure 1: Exercises
Fall 2013, David Matuszek
Write and test the following functions. Please be sure to get the spelling and capitalization right, and the right number and types of parameters, in order to make testing them feasible.
These are mostly unrelated exercises, to give you some experience with Clojure syntax. The earlier ones depend on recursion, while the latter are best done using some of Clojure's second-order functions.
In some cases, for example reversing a list, you may find Clojure functions that already do exactly what you want. Please don't use them, but rather write the functions yourself.
Most of these functions are defined to work with lists, because my experience in Lisp has been almost entirely with lists. If your functions works with lists, they will probably also work with other kinds of sequences.
You don't need higher-order functions to program these, but if you see an opportunity to use them, go ahead. Generally, the purpose is to get you used to writing recursive functions the Clojure way.
(atomic? v)
true
if v
is not any kind of a sequence (check with seq?
), and false
otherwise.(collatz n)
n
. If n
is 1
, return 1
; else if n
is even, return collatz(n
/2); else return collatz(3n
+ 1). (Yes, this is just a complicated way to compute 1
.)(lookup key list-of-pairs)
key
and a list of (key value)
pairs, return the value
that corresponds to the key
, or nil
if there is no such pair. You can assume that there is only one such pair.(my-count lst)
lst
. For example,
(a (b c (d e)) f)
has 3 top level elements; (b c (d e))
is a single top-level element. (a b () d)
has 4 top-level elements.(count-all lst)
lst
, at all levels. For example, (a (b c () (25) nil) ())
a
, b
, c
, 25
, and nil
.(my-drop n lst)
lst
with the first n
elements removed. For example, (my-drop 3 '(a b c d e))
should return (d e))
. If n
is equal to or greater than the length of the list lst
, return the empty list, ()
.(my-take n lst)
n
elements of lst
. If lst
has fewer than n
elements, the result is just lst
.(shallow-reverse lst)
lst
. For example, the list
(1 2 (3 4))
becomes the sequence
((3 4) 2 1)
.(remove-duplicates lst)
lst
. For example, given (1 2 3 1 4 1 2)
, remove-duplicates
returns a sequence containing the elements (1 2 3 4)
, in some order. (my-flatten lst)
lst
with all inner parentheses (or brackets) removed, returning a "flat" list of values. For example, if lst
is (1 (2 3) ( ) (( )) :a)
,
the result should be (1 2 3 :a )
. Hint: Use the predicate list?
. (my-merge lst1 lst2)
lst1
is (3 7 12 19 19 25 30)
and lst2
is (4 7 10 12 20)
, the result should be (3 4 7 7 10 12 12 19 19 20 25 30)
.(deep-reverse lst)
L
at all levels. For example, if lst
is (:a (:b :c (:d)) :e)
, deep-reverse
should return (:e ((:d) :c :b) :a)
.(eliminate value lst)
lst
with all occurrences of
the value
removed, at all levels. For example, if lst
is (:a :b (:b :c :d (:a (:b))) :e)
, (eliminate :b lst)
should return(:a (:c :d (:a ())) :e)
. Note that the value
may be any value, for example, a sequence.These are all probably best done with higher-order functions, so please use them wherever they seem to work.
(zap-gremlins text)
filter
.(rot-13 text)
(int ch)
and (char n)
. Hint: map
.(sqrt n)
n
, using Newton's method. That is, choose some arbitrary number, say 2, as the initial approximation r
to the square root; then to get the next approximation, compute the average of r
and n/r
.
Continue until you have five significant digits to the right of the
decimal point. Do this by taking an infinite series of approximations,
iterate
. (longest-collatz lo hi)
lo
to hi
(including both end points) takes the longest to converge. If two values take equally long to converge, return either value.(divisors-of n)
n
, returns the divisors of n
, other than 1 and n
itself. For example, 12 has divisors (2, 3, 4, 6)
. Hint: mod
and filter
.Write, in a separate file, unit tests for all your methods. Since we
haven't talked about testing yet, here's a model for you to follow.
Notice the use of deftest
and is
.
(ns user (:use clojure.test))
(deftest test-shallow-reverse
(is (= '(3 2 1) (shallow-reverse '(1 2 3))))
(is (= '(5 (3 4) 2 1) (shallow-reverse '(1 2 (3 4) 5))))
(is (= () (shallow-reverse ()))) )
(deftest test-deep-reverse
(is (= '(3 2 1) (deep-reverse '(1 2 3))))
(is (= '(5 (4 3) 2 1) (deep-reverse '(1 2 (3 4) 5))))
(is (= () (deep-reverse ()))) )
(run-tests)
Zip and turn in your exercises.clj
and exercises-test.clj
files by 6am, Wednesday September 25 As always, only files submitted to Canvas will be accepted. I do not accept assignments submitted by email.
Late penalties: There will be a 10 point penalty (out of 100 points) for programs between one minute and one week late, and a 25 point penalty for programs later than one week. At some unspecified time after one week we will stop accepting assignments.