c - 将比较运算符作为 char 与 scanf 并在 if 中使用

Question

#include<stdio.h>
int main()
{
    int a,b;
    char c;

    printf("Enter value for a and b ");
    scanf("%d %d ",a,b);
    printf("Enter c(<) or c(>) for comparison");
    scanf(" %c ",c);

    if(a ? b)
    {
        printf("%d ",a);
    }
}

我想从 scanf 中获取 char c 并将其放在 ? ，并且我想以这种方式运行 if 语句，是否可以以任何方式运行？

Answer 1

不可能像 C 那样在运行时动态更改比较运算符。

相反，您可以使用如下所示的方法(我还对代码添加了一些修复，在注释中进行了解释):

#include<stdio.h>
int main()
{
    int a, b;
    char c;

    printf("Enter value for a and b ");
    // No spaces neeeded after specifiers, otherwise the user have to input additional data
    // Pointers to the variables have to be passed to scanf
    scanf("%d%d", &a, &b);
    printf("Enter c(<) or c(>) for comparison ");
    // A single space needed before %c , to discard previous newline
    scanf(" %c", &c);

    int condition = 0; // initial: false
    // For every of the operators, assign the comparison result to 'condition'
    if (c == '<')
        condition = (a < b);
    else if (c == '>')
        condition = (a > b);
    else
        printf("Unknown operator: %c\n", c);

    // Test for condition
    if (condition)
    {
        printf("%d\n",a);
    }
    // Add a return statement
    return 0;
}