C Primer Plus(第6版)第十四章复习题答案

1.正确的关键字是struct，最后一条声明语句以及结构模板有花括号要有分号。

2.输出如下

6 1
22 Spiffo Road
S p

3.struct month
{
char name[10];
char abbrev[4];
int days;
int monumb;
};

struct month months[12] = 
{
	{"January", "jan", 31, 1},
	{"February", "feb", 28, 2},
	{"March", "mar", 31, 3},
	{"April", "apr", 30, 4},
	{"May", "may", 31, 5},
	{"June", "jun", 30, 6},
	{"July", "jul", 31, 7},
	{"August", "aug", 31, 8},
	{"September", "sep", 30, 9},
	{"October", "oct", 31, 10},
	{"November", "nov", 30, 11},
	{"December", "dec", 31, 12}
}

extern struct month months[];
int days(int month)
{
	int index, total;
	if (month < 1 || month > 12)
		return -1; // error signal
	else
	{
		for (index = 0, total = 0; index < month; index++)
			total += months[index].days;
		return (total);
	}
}

a.要包含strings.头文件，提供strc()的原型
typedef struct lens
{
	float foclen;
	float fstop;
	char brand[30];
} LENS;
LENS bigEye[10];
bigEye[2].foclen = 500;
bigEye[2].fstop = 2.0;
strcpy(bigEye[2].brand, "Remarkatar");

b.LENS bigEye[10] = { [2] = {500, 2, "Remarkatar"} };

a.
6
Arcturan
cturan

b.使用结构名和指针
deb.title.last
pb->title.last

c.下面是一个版本：
#include <stdio.h>
#include "starflok.h"  // 让结构定义可用
void prbem(const struct bem * pbem) 
{
  	printf("%s %s a %d -limited %s.\n", pb->title.first, 
  	pbem->title.last, pbem->limbs, pbem->type);
}

a.willie.born
b.pt->born
c.scanf("%d", &willie.born);
d.scanf("%d", &pt->born);
e.scanf("%s", willie.name.lname);
f.scanf("%s", pt->name.lname);
g.willie.name.fname[2]
h.strlen(willie.name.fname) + strlen(willie.name.lname)

下面是一种方案：
struct car
{
	char name[20];
	float hp;
	float epampg;
	flaot wbase;
	int year;
};

10

应该这样建立函数
struct gas 
{
	float distance;
	float gals;
	float mpg;
};

struct gas mpgs(struct gas trip)\
{
	if (trip.gals > 0)
		trip.mpg = trip.distance / trip.gals;
	else
		trip.mpg = -1.0;
	return trip;
}

void set_mpgs(struct gas * ptrip)
{
	if (ptrip->gals > 0)
		ptrip->mpg = ptrip->distance / ptrip->gals;
	else 
		ptrip->mpg = -1.0;
}

注意第一个函数不能直接改变主调程序中的值，所以必须用返回值才能传递信息。
struct gas idaho = {430.0, 14.8};
idahp = mpgs(idaho);
但是第二个函数可以直接访问最初的结构：
struct gas ohio = {583, 17,6};
set_mpgs(&ohio);

11.enum choices {no, yes, maybe};

12.char * (*pfun) (char *, char);

13.``

double sum(double, double);
double diff(double, double);
double times(double, double);
double divide(double, double);
doube (*pf[4]) (double, double) = {sum, diff, times, divide};

或者用更简单的形式，把代码中的最后一行替换成：
typedef double (*ptype) (double, double);
ptype pf1[4] = {sum, diff, times, divide};

调用diff()函数
pf1[1] (10.0, 2.5); // 第1种表示法
(*pf1[1]) (10.0, 2.5); // 等价表示法