c - 为什么 switch 语句在这个 C 计算器中显示默认值？

Question

当我运行这个程序时，它会忽略 switch 语句中的所有内容，并显示 default。我正在使用 Code::Blocks。请向我解释为什么会遇到这个逻辑错误，也许这是 Code::Blocks 中的错误，而不是代码中的错误 - 我应该在另一个 IDE 上尝试吗？

#include <stdio.h>
    int main()
    {
        double a,b;
        int choose,subtract,divide;
        printf("My first Calculater in c\n");
        printf("\n");
        printf("Enter your two numbers\n");
        scanf("%lf",&a);
        scanf("%lf",&b);
        printf("Please choose an operation\n");
         printf("1.add two no.(s)\n");
         printf("2.subtract two no.(s)\n");
         printf("3.multiply two no.(s)\n");
         printf("4.divide two no.(s)\n");
         printf("please choose an operation ");
           scanf("%lf", &choose);

    switch(choose){

     case 1:
        printf("sum of a+b is : %lf\n",(a+b));
        break;

     case 2:
        printf("1.a-b?\n");
        printf("2.b-a?\n");
        scanf("%d", &subtract);
        switch(subtract)
        {
         case 1:
            printf("\ndiff of a-b is : %lf",(a-b));
            break;

         case 2:
            printf("\ndiff of b-a is : %lf",(b-a));
             break;

        }
     case 3:
            printf("\nproduct of a*b is : %lf",(a*b));
             break;

     case 4:
            printf("\n1.divide a/b?,a!=0");
            printf("\n2.divide b/a?,b!=0");
            scanf("%d", &divide);
            switch(divide)
            {
            case 1:
                if(b==0)
                    printf("\ndivision by zero is undefined");
                    else
                       printf("\nquotient of a/b is : %lf",(a/b));
                    break;
            case 2:

                if(a==0)
                    printf("\ndivision by zero is undefined");
                    else
                        printf("\nquotient of b/a is : %lf",(b/a));
                        break;
           }
     default:
          printf("please choose either 1,2,3 or 4 options\n");
        }

    }

Answer 1

您正在双读选择

scanf("%lf", &choose);

改为读取小数

scanf("%d", &choose);