Starting code for the problem set:
(ns traverse
(:require clojure.test))
(use 'clojure.repl)
(use 'clojure.test)
;; traverse returns a function that can be used
;; as map, filter, etc
(defn traverse [combine op seed]
(fn [x] (if (empty? x)
seed
(combine (op (first x)) ((traverse combine op seed) (rest x))))))
(def mapsquare (traverse cons #(* %1 %1) []))
(def sumlist (traverse + (fn [x] x) 0))
(deftest test-mapsquare
(is (= (mapsquare []) []))
(is (= (mapsquare [2 3 4]) [4 9 16]))
)
(deftest test-sumlist
(is (= (sumlist []) 0))
(is (= (sumlist [1 2 3]) 6))
)
Using traverse, define and test the following functions:
count to count the elements in a collection (make sure to test it on non-integers)remove5 to remove all 5s from a collection of numbers, return a vector.countChars to take a collection of strings and return a vector of lengths of these strings.reverse to reverse a collection; return a vector.
Write a function nested-traverse that works just
like traverse, except it traverses collections with
sub-collections of arbitrary nesting, such as this one:
[2 [3 4] 1 [[4]]]
For simplicity you may assume that all your collections are vectors.
nested-traverse should be used exactly
as traverse: when provided the
functions combine and op and a seed, it
returns a function that traverses the nested collection,
applying op to every element, combining the results
using combine, and returning seed for every
empty collection.
Use the function coll? to check if an element is a
collection.
Below are two examples of using nested-traverse that may
be used as test cases (more test cases are needed).
(def nested-mapsquare (nested-traverse cons #(* %1 %1) []))
(deftest test-nested-mapsquare
(is (= (nested-mapsquare []) []))
(is (= (nested-mapsquare [2 3 4]) [4 9 16]))
(is (= (nested-mapsquare [2 [3 4] 1 [[4]]]) [4 [9 16] 1 [[16]]]))
)
(def nested-sumlist (nested-traverse + (fn [x] x) 0))
(deftest test-nested-sumlist
(is (= (nested-sumlist []) 0))
(is (= (nested-sumlist [1 2 3]) 6))
(is (= (nested-sumlist [2 [3 4] 1 [[4]]]) 14))
)
Submit your function and all your test cases.
Using nested-traverse, define and test the following three
functions:
nested-reverse that reverses every collection, but
otherwise preserves the nested structure. For instance, for the
nested [2 [3 4] 1 [[4]]] it returns [[[4]] 1 [4
3] 2]nested-flatten that returns a one-dimensional vector
of all elements in a nested structure in the order in which they are
encountered. For the same example the result is [2 3 4 1
4].nested-reverse-flatten that flattens the collection
into a vector while reversing the order of the elements. The result
for the above example is [4 1 4 3 2].Exercise 3.2 parts a,b p. 40-41.