C学生作业，'％f'需要'float *'类型的参数，但参数2的类型为'double *'

Question

我正在完成任务，我收到了这个警告：

C4_4_44.c:173:2: warning: format ‘%f’ expects argument of type ‘float *’, 
but argument 2 has type ‘double *’ [-Wformat]

变量在main中声明为：

double carpetCost;

我将该函数称为：

getData(&length, &width, &discount, &carpetCost);

这是功能：

void getData(int *length, int *width, int *discount, double *carpetCost)

{

    // get length and width of room, discount % and carpetCost as input

    printf("Length of room (feet)? ");

    scanf("%d", length);

    printf("Width of room (feet)? ");

    scanf("%d", width);

    printf("Customer discount (percent)? ");

    scanf("%d", discount);

    printf("Cost per square foot (xxx.xx)? ");

    scanf("%f", carpetCost);

    return;

} // end getData

这让我抓狂，因为这本书说你不使用＆amp;在

scanf("%f", carpetCost); 

从您传递它的函数访问它时是参考。

我在这里做错了什么想法？

Answer 1

更改

scanf("%f", carpetCost);

与

scanf("%lf", carpetCost);

%f转换规范用于float *参数，%lf参数需要double *。

Answer 2

使用%lf规范代替double *参数。

scanf("%lf", carpetCost); 

Answer 3

Use %lf instead of %f if you are scanning a double type of variable.
you can check this in detail also about %lf & %f from the discussed thread's link


http://stackoverflow.com/questions/210590/why-does-scanf-need-lf-for-doubles-when-printf-is-okay-with-just-f