# racketeering / a2functions.scm

 ``` 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55``` ```#lang racket ; CS152 Assignment Two ; 1) (10 Points) Define a function p to compute the polynomial ; p(x) = 1 + x + x^2/2 + x^3/6. ; Note that this polynomial approximates the function e^x. ; You needn't compute the function in the most efficient possible way. (define (p x) (+ 1.0 x (/ (* x x) 2.0) (/ (* x x x) 6.0))) ; 2) (15 points) Define a function symbol-append that takes two arguments. ; If both arguments are symbols, the function is to return a symbol ; representing the concatenation of the two symbols. Otherwise the function ; is to return #f. So for example (symbol-append 'hello 'there) should return ; the symbol hellothere. (define (symbol-append a b) (if (and (symbol? a) (symbol? b)) (string->symbol (string-append (symbol->string a) (symbol->string b))) #f)) ; 3) (15 points) Define a predicate list-of-nonempty-strings? of one argument ; that returns #t if and only if its argument is a list and every member of ; the list is a nonempty string. (define (list-of-nonempty-strings? lst) (and (and (string? (car lst)) (> (string-length (car lst)) 0)) (or (null? (cdr lst)) (list-of-nonempty-strings? (cdr lst))))) ; Define a function first-string that takes a list of nonempty strings and ; returns the first string in case-insensitive lexicographical order. ; If the list is empty or is not a list of strings, you are to return the ; empty string. (define (first-string lst) (define (radix-sort-string-list lst) (define (string-list->char-list lst) (if (null? lst) '() (append (list (string->list (car lst))) (string-list->char-list (cdr lst)))) (if (list-of-nonempty-strings? lst) (car (radix-sort-string-list lst)) '())) ; (10 points) Define a function longest-satisfying-prefix that takes a list and a unary predicate as argument and returns a copy of the input list, up to but not including the first member that fails to satisfy the predicate. So for example (longest-satisfying-prefix '(16 8 4 2 1) even?) should return (16 8 4 2), as should (longest-satisfying-prefix '(16 8 4 2) even?). ; (10 points) Define a boolean-valued function alist-simple? that takes an association list, and returns #t if and only if all of the members of the assocation list have distinct cars. That is, the function is to return #f precisely when the association list can be replaced by a shorter equivalent association list. ```