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Chapter 16 Answers to Selected Exercises 2. [was #2; modified] (a) struct { double real, imaginary; } c1, c2, c3; (b) struct { double real, imaginary; } c1 = {0.0, 1.0}, c2 = {1.0, 0.0}, c3; (c) Only one statement is necessary: c1 = c2; (d) c3.real = c1.real + c2.real; c3.imaginary = c1.imaginary + c2.imaginary; 4. [was #4; modified] (a) typedef struct { double real, imaginary; } Complex; (b) Complex c1, c2, c3; (c) Complex make_complex(double real, double imaginary) { Complex c; c.real = real; c.imaginary = imaginary; return c; } (d) Complex add_complex(Complex c1, Complex c2) { Complex c3; c3.real = c1.real + c2.real; c3.imaginary = c1.imaginary + c2.imaginary; return c3; } 11. [was #10; modified] The a member will occupy 8 bytes, the union e will take 8 bytes (the largest member, c, is 8 bytes long), and the array f will require 4 bytes, so the total space allocated for s will be 20 bytes. 14. [was #12; modified] (a) double area(struct shape s) { if (s.shape_kind == RECTANGLE) return s.u.rectangle.height * s.u.rectangle.width; else return 3.14159 * s.u.circle.radius * s.u.circle.radius; } (b) struct shape move(struct shape s, int x, int y) { struct shape new_shape = s; new_shape.center.x += x; new_shape.center.y += y; return new_shape; } (c) struct shape scale(struct shape s, double c) { struct shape new_shape = s; if (new_shape.shape_kind == RECTANGLE) { new_shape.u.rectangle.height *= c; new_shape.u.rectangle.width *= c; } else new_shape.u.circle.radius *= c; return new_shape; } 15. [was #14] (a) enum week_days {MON, TUE, WED, THU, FRI, SAT, SUN}; (b) typedef enum {MON, TUE, WED, THU, FRI, SAT, SUN} Week_days; 17. [was #16] All the statements are legal, since C allows integers and enumeration values to be mixed without restriction. Only (a), (d), and (e) are safe. (b) is not meaningful if i has a value other than 0 or 1. (c) will not yield a meaningful result if b has the value 1. Answers to Selected Programming Projects 1. [was #6; modified] #include <stdio.h> #define COUNTRY_COUNT \ ((int) (sizeof(country_codes) / sizeof(country_codes[0]))) struct dialing_code { char *country; int code; }; const struct dialing_code country_codes[] = {{"Argentina", 54}, {"Bangladesh", 880}, {"Brazil", 55}, {"Burma (Myanmar)", 95}, {"China", 86}, {"Colombia", 57}, {"Congo, Dem. Rep. of", 243}, {"Egypt", 20}, {"Ethiopia", 251}, {"France", 33}, {"Germany", 49}, {"India", 91}, {"Indonesia", 62}, {"Iran", 98}, {"Italy", 39}, {"Japan", 81}, {"Mexico", 52}, {"Nigeria", 234}, {"Pakistan", 92}, {"Philippines", 63}, {"Poland", 48}, {"Russia", 7}, {"South Africa", 27}, {"South Korea", 82}, {"Spain", 34}, {"Sudan", 249}, {"Thailand", 66}, {"Turkey", 90}, {"Ukraine", 380}, {"United Kingdom", 44}, {"United States", 1}, {"Vietnam", 84}}; int main(void) { int code, i; printf("Enter dialing code: "); scanf("%d", &code); for (i = 0; i < COUNTRY_COUNT; i++) if (code == country_codes[i].code) { printf("The country with dialing code %d is %s\n", code, country_codes[i].country); return 0; } printf("No corresponding country found\n"); return 0; } 3. [was #8] #include <stdio.h> #include "readline.h" #define NAME_LEN 25 #define MAX_PARTS 100 struct part { int number; char name[NAME_LEN+1]; int on_hand; }; int find_part(int number, const struct part inv[], int np); void insert(struct part inv[], int *np); void search(const struct part inv[], int np); void update(struct part inv[], int np); void print(const struct part inv[], int np); /********************************************************** * main: Prompts the user to enter an operation code, * * then calls a function to perform the requested * * action. Repeats until the user enters the * * command 'q'. Prints an error message if the user * * enters an illegal code. * **********************************************************/ int main(void) { char code; struct part inventory[MAX_PARTS]; int num_parts = 0; for (;;) { printf("Enter operation code: "); scanf(" %c", &code); while (getchar() != '\n') /* skips to end of line */ ; switch (code) { case 'i': insert(inventory, &num_parts); break; case 's': search(inventory, num_parts); break; case 'u': update(inventory, num_parts); break; case 'p': print(inventory, num_parts); break; case 'q': return 0; default: printf("Illegal code\n"); } printf("\n"); } } /********************************************************** * find_part: Looks up a part number in the inv array. * * Returns the array index if the part number * * is found; otherwise, returns -1. * **********************************************************/ int find_part(int number, const struct part inv[], int np) { int i; for (i = 0; i < np; i++) if (inv[i].number == number) return i; return -1; } /********************************************************** * insert: Prompts the user for information about a new * * part and then inserts the part into the inv * * array. Prints an error message and returns * * prematurely if the part already exists or the * * array is full. * **********************************************************/ void insert(struct part inv[], int *np) { int part_number; if (*np == MAX_PARTS) { printf("Database is full; can't add more parts.\n"); return; } printf("Enter part number: "); scanf("%d", &part_number); if (find_part(part_number, inv, *np) >= 0) { printf("Part already exists.\n"); return; } inv[*np].number = part_number; printf("Enter part name: "); read_line(inv[*np].name, NAME_LEN); printf("Enter quantity on hand: "); scanf("%d", &inv[*np].on_hand); (*np)++; } /********************************************************** * search: Prompts the user to enter a part number, then * * looks up the part in the inv array. If the * * part exists, prints the name and quantity on * * hand; if not, prints an error message. * **********************************************************/ void search(const struct part inv[], int np) { int i, number; printf("Enter part number: "); scanf("%d", &number); i = find_part(number, inv, np); if (i >= 0) { printf("Part name: %s\n", inv[i].name); printf("Quantity on hand: %d\n", inv[i].on_hand); } else printf("Part not found.\n"); } /********************************************************** * update: Prompts the user to enter a part number. * * Prints an error message if the part can't be * * found in the inv array; otherwise, prompts the * * user to enter change in quantity on hand and * * updates the array. * **********************************************************/ void update(struct part inv[], int np) { int i, number, change; printf("Enter part number: "); scanf("%d", &number); i = find_part(number, inv, np); if (i >= 0) { printf("Enter change in quantity on hand: "); scanf("%d", &change); inv[i].on_hand += change; } else printf("Part not found.\n"); } /********************************************************** * print: Prints a listing of all parts in the inv array, * * showing the part number, part name, and * * quantity on hand. Parts are printed in the * * order in which they were entered into the * * array. * **********************************************************/ void print(const struct part inv[], int np) { int i; printf("Part Number Part Name " "Quantity on Hand\n"); for (i = 0; i < np; i++) printf("%7d %-25s%11d\n", inv[i].number, inv[i].name, inv[i].on_hand); } Copyright © 2008, 1996 W. W. Norton & Company, Inc. All rights reserved.

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