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--- cs330_f2016:racketlists [2016/08/31 18:49]
morse
+++ cs330_f2016:racketlists [2021/06/30 23:42]
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-====Objective:====
-Learn the basics of the Racket lists and various patterns of recursion:
-  * List operators
-  * Natural recursion
-  * Common patterns for recursive list-processing operations
-  * Using auxiliary variables
-----
-====Preparation:====
-You will again use DrRacket, which you should have downloaded and installed for the previous lab.
-----
-====Deliverables:====
-For this lab, you will need to implement the following functions and data structures in Racket:
-  * ''check-temps1''
-  * ''check-temps''
-  * ''convert''
-  * ''duple''
-  * ''average''
-  * ''convertFC''
-  * ''eliminate-larger''
-  * ''get-nth''
-  * ''find-item''
-=== check-temps1 ===
-<code racket>
-(define (check-temps1 temps) ...)
-</code>
-where ''temps'' is a list of numbers representing temperatures and the result is a boolean indicating whether all of the temperatures are with the range 5 to 95 inclusive.
-For example, ''(check-temps1 (list 80 92 56))'' returns true, and ''(check-temps1 (list 80 99 56))'' returns false.
-=== check-temps1 ===
-<code racket>
-(define (check-temps temps low high) ...)
-</code>
-where ''temps'' is a list of numbers representing temperatures and the result is a boolean indicating whether all of the temperatures are with the range ''low'' to ''high'' inclusive.
-For example, ''(check-temps some-list-of-temps 5 95)'' should work just like ''(check-temps1 some-list-of-temps)''.
-Suggestion: Yes, you could code ''check-temps1'' to just call your more general ''check-temps''. But try to code ''check-temps1'' first to see the basic pattern, then think about how to generalize it to ''check-temps''.
-=== convert ===
-<code racket>
-(define (convert digits) ...)
-</code>
-where ''digits'' is a list of digits (each between 0 and 9) and the result is the integer equivalent of these interpreted as a list of digits of a number in reverse order.
-For example, ''(convert (list 1 2 3))'' should return the number 321.
-=== duple ===
-<code racket>
-(define (duple lst) ...)
-</code>
-where ''lst'' is a list of any type of values, and the result is a list of two-element lists that has each value duplicated.
-For example, ''(duple (list 1 2 3))'' returns the list ''( (1 1) (2 2) (3 3) )''.
-Hint: Be careful when to use ''list'' and when to use ''cons''.
-=== average ===
-<code racket>
-(define (average lst) ...)
-</code>
-where ''lst'' is a list of numbers, and the result is the average of these numbers.
-For example, ''(average (list 1 2 3 4))'' returns 2.5.
-=== convertFC ===
-<code racket>
-(define (convertFC temps) ...)
-</code>
-where ''temps'' is a list of numbers representing temperatures in Fahrenheit, and the result is a list representing the same values in Celsius.
-For example, ''(convertFC (list 32 50 212))'' returns ''(0 10 100)''.
-=== eliminate-larger ===
-<code racket>
-(define (eliminate-larger lst) ...)
-</code>
-where ''lst'' is a list of numbers, and the result is the same list but with all values larger than any subsequent ones removed.
-For example, ''(eliminate-larger (list 1 2 3 9 4 5))'' returns ''(1 2 3 4 5)''.
-Hint: try using a helper function.
-=== get-nth ===
-<code racket>
-(define (get-nth lst n) ...)
-</code>
-where ''lst'' is a list of arbitrary types and ''n'' is a non-negative number less than the length of the list, and the result is the nth item of the list using zero-based indexing.
-For example ''(get-nth (list 1 2 3 4) 2)'' returns the value 3.
-Note: You must code this recursively and not use any other built-in Racket functions for such indexing, nor can you simply convert it to a vector and then do random access.
-=== find-item ===
-<code racket>
-(define (find-item lst target) ...)
-</code>
-where ''lst'' is a list of numbers and ''target'' is a number, and the result is the position (using zero-based indexing) at which ''target'' first appears in the list, or -1 if it doesn't appear.
-For example, ''(find-item (list 1 2 3 4) 3)'' returns the value 2, and ''(find-item (list 1 2 3 4) 42)'' returns -1.
-Hint: consider using an auxiliary variable.
-----
-====Notes:====
-You again **do not** need to bulletproof the code to enforce proper inputs.
-Your code only needs to return correct values given correct inputs.
-----
-====Hints:====
-You may want to again use the Step button to walk through your code and watch the equivalent sequence of substitutions that are performed.  This is particularly useful in tracing the recursion and watching what's happening to the parameters.

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