C第10章-----通过引用传递

#include <stdio.h>

#include <math.h>

void metersToFeetAndInches(double meters,unsigned int *ftPtr,double *inPtr){

//这个函数假定meters的值是非负数

//将meters变量的值转化为feet的值，类型为浮点数

double rawFeet = meters * 3.281;  //e.g. 2.4536

printf("rawFeet: %lf\n", rawFeet);

//计算类型为无符号的整形的feet变量的值

unsigned int feet = (unsigned int)floor(rawFeet);

printf("ftPtr: %p\n", ftPtr);

printf("*ftPtr: %d\n", *ftPtr);

//将feet变量的值存储在提供的地址里

//先检查指针是否为NULL

if(ftPtr){

printf("------------------------------------------\n");

printf("Storing %u to the address %p\n",feet ,ftPtr);

*ftPtr = feet;

printf("ftPtr: %p\n", ftPtr);

printf("*ftPtr: %d\n", *ftPtr);

}

//计算英寸

double fractionalFoot = rawFeet - feet;

double inches = fractionalFoot * 12.0;

printf("fractionalFoot: %lf\n", fractionalFoot);

printf("inches: %lf\n", inches);

printf("------------------------------------------\n");

//将inches变量的值保存到传入的地址

//先检查指针是否为NULL

if(inPtr){

printf("Storing %.2f to the address %p\n", inches, inPtr);

*inPtr = inches;

printf("inPtr: %p\n", inPtr);

printf("*inPtr: %lf\n", *inPtr);

}

}

int main(int argc, const char * argv[]) {

double meters = 3.0;

unsigned int feet;

double inches;

metersToFeetAndInches(meters, &feet, &inches);

printf("%.1f meters is equal to %d feet and %.1f inches.",meters,feet,inches);

return 0;

}

结果：

rawFeet: 9.843000

ftPtr: 0x7ffeefbff514

*ftPtr: 0

------------------------------------------

Storing 9 to the address 0x7ffeefbff514

ftPtr: 0x7ffeefbff514

*ftPtr: 9

fractionalFoot: 0.843000

inches: 10.116000

------------------------------------------

Storing 10.12 to the address 0x7ffeefbff508

inPtr: 0x7ffeefbff508

*inPtr: 10.116000

3.0 meters is equal to 9 feet and 10.1 inches.Program ended with exit code: 0