c - 除以小数时无法得到正确答案

Question

这是我的第一门编码类(class)。当我在选择中选择数字 3 时出现错误。也就是说，如果我将 12 除以 2，程序会给出正确的输出，但是，如果我将 10.4 除以 2，程序输出就会进入循环，直到我停止程序。

#include <stdio.h>

int main() {
    /* variable definition: */

    int intValue, menuSelect, results;
    float shrink;

    intValue = 1; 
    // While a positive number
    while (intValue > 0) {    
        printf("Enter a positive Integer\n: ");
        scanf("%d", &intValue);
        {
            printf("Enter 1 to calculate Square, 2 to Calculate Cube, or 3 to divide  input by 2, to end program enter a negative integer.\n: ");
            scanf("%d", &menuSelect);
            if (menuSelect == 1) {
                // Call the Square Function
                results = Square(intValue);
                printf("Square of %d is %d\n", intValue, results);
            } else
            if (menuSelect == 2) {
                // Call the Cube function
                results = Cube(intValue);
                printf("Cube of %d is %d\n", intValue, results);
            } else
            if (menuSelect == 3) {
                // Call the Divisor function
                results = Shrink (intValue);
                printf("The quotient of %d is %d\n", intValue, results);
            } else 
                printf("Invalid menu item, only 1, 2 or 3 is accepted\n");
        }
    }   
    return 0;
}

/* function returning the Square of a number */
int Square(int value) {
    return value * value;
}

/* function returning the Cube of a number */
int Cube(int value) {
    return value * value * value;
}

/* function returning the quotient of a number */
int Shrink(int value) {
    return (double)value / 2;
}

Answer 1

首先是什么

floatshrink;

在 main 的第二行，你的程序甚至不应该编译。

你遇到的问题是

1)你不能在你的程序中输入 float 。您的变量都是整数，而您只扫描整数。

int intValue, menuSelect, results;

//(...)

scanf("%d", &intValue);

2) 您的函数只返回整数，因此无论如何您都会丢失小数部分。

int Shrink(int value)
{
return (double)value/2;

}

3) 不要忘记你的标题!!编译器需要知道会发生什么

double Square(double value);

/* function returning the Cube of a numnber */
double Cube(double value);

/* function returning the quotient of a number */
double Shrink(double value);

你们最后遇到了一些关于缩进的基本问题，别担心，你们很快就会掌握的这是更正后的版本

#include <stdio.h>
#include <stdlib.h>


double Square(double value);

/* function returning the Cube of a numnber */
double Cube(double value);

/* function returning the quotient of a number */
double Shrink(double value);


int main (void )
{
    /* variable definition: */

    float numer_input,results;
    int menuSelect;
    //floatshrink; (no idea what this is)

    numer_input = 1; //you could use a do while statement to avoid this 
    // While a positive number
    while ( numer_input> 0)
    {    
        printf ("Enter a positive Integer\n: ");
        scanf("%f", &numer_input);


        printf ("Enter 1 to calculate Square, 2 to Calculate Cube, or 3 to divide  input by 2, to end program enter a negative integer.\n: ");
        scanf("%d", &menuSelect);
        if (menuSelect == 1)
        {
        // Call the Square Function
            results = Square(numer_input);
            printf("Square of %f is %f\n",numer_input, results);
        }
        else if (menuSelect == 2)
        {
        // Call the Cube function
            results = Cube(numer_input);
            printf("Cube of %f is %f\n",numer_input, results);
        }
        else if (menuSelect == 3)
        {
        // Call the Divisor function
            results = Shrink (numer_input);
            printf("The quotient of %f is %f\n", numer_input, results);
        }
        else 
            printf("Invalid menu item, only 1, 2 or 3 is accepted\n");

    }   

    return 0;
}

/* function returning the Square of a number */
double Square(double value){
    return value*value;
}

/* function returning the Cube of a numnber */
double Cube(double value){
    return value*value*value;
}

/* function returning the quotient of a number */
double Shrink(double value){
    return (double)value/2;
}

最后，我建议使用 switch 语句，因为代码看起来比 if 和 else if 更清晰，但这是个人喜好问题。