使用 scanf 读取浮点值时出错

Question

我在读取此 C 代码片段的两个浮点值时遇到问题：

#include<stdio.h>
long double add(long double a, long double b)
{ return a+b; }

int main()
{
 long double a, b;
 printf("Input two FP values: ");
 //Here scanf isn't reading the 2nd value.
 scanf("%lf %lf", &a, &b);
 printf("%lf", add(a,b));
 return 0;
}

当提供 2 和 4 作为输入时，程序显示 0.000000 作为输出。

Answer 1

了解如何在编译器中启用警告并且不要忽略它们。

a.c:10:11: warning: format ‘%lf’ expects argument of type ‘double *’, but argument 2 has type ‘long double *’ [-Wformat=]

a.c:10:15: warning: format ‘%lf’ expects argument of type ‘double *’, but argument 3 has type ‘long double *’ [-Wformat=]

a.c:11:12: warning: format ‘%lf’ expects argument of type ‘double’, but argument 2 has
type ‘long double’ [-Wformat=]

Answer 2

%lf用于读取double，而%Lf用于读取long double。因此，如果您将 %lf 替换为 %Lf，那么通过您的代码，它将正常工作。

demo

使用 scanf 读取浮点值时出错

Error while reading floating point values using scanf

c

floating-point

scanf

format-specifiers