程序不向函数返回值

Question

我正在尝试制作一个牛顿第二定律计算器，当我输入计算值时，没有任何反应。我不确定它们是否没有返回到主函数或什么。我想要做的是让用户输入一个字符，然后由一个包含 switch 语句的函数获取，在 switch 语句的情况下，函数调用执行算术的函数，然后这些函数将返回一个值switch 函数和 switch 函数将返回一个值给 main 函数，然后将值打印到屏幕上。

// Newtons2ndlaw.cpp : This file contains the 'main' function. Program 
execution begins and ends there.
//

#include "pch.h"
#include <stdio.h>
#include <stdlib.h>
#include<iostream>

void varselect(char, float *);

void force(float *);

void acceleration(float *);

void mass(float *);

int main()


{

    float eqvalue;
    char operation;

    printf("Welcome to Newtons 2nd law solver!\n");

    system("PAUSE");

    printf("Would you like to solve for a Force, Acceleration or Mass?\nType 'F'(for force), 'A'(for acceleration), 'M'(for mass) to select a variable\n");

    scanf_s("%c", &operation,1);
    if (operation == 'f' || operation == 'F' || operation == 'a' || operation == 'A' || operation == 'm' || operation == 'M')           //logic for determing what the user entered
    {}
    else
    {
        printf("Please enter a valid character.");
    }

     varselect(operation,&eqvalue);             //function call to receive float value from varselect function

     if (operation == 'f' || operation == 'F')              //{
     {
         printf("The force = %f",eqvalue);
     }
                                                                //this block determines what character string to display with calculated float value                                    
     else if (operation == 'a' || operation == 'A')                         
     {
         printf("The acceleration = %f", eqvalue);
     }

     else if (operation == 'm' || operation == 'M')
     {
         printf("the Mass = %f", eqvalue);
     }
}                                                           //}

void varselect(char x, float *j)                            
                                                                    //this function recieves the user inputed char value and returns the calculated float value to function call. 
{                                                                   //switch allows program to "understand" users unwillingness to press shift before a,f,m like printf statement tells them to do.
    switch (x)                                                      // also allows each variable to call its own function.
    {
    case 'f':
        float getval;
        force(&getval);
        *j = getval;
        return;
        break;
    }

    switch (x)
    {
    case 'F':
        float getval;
        force(&getval);
        *j = getval;
        return;
        break;
    }

    switch (x)
    {
    case 'a':
        float getval;
        acceleration(&getval);
        *j = getval;
        return;
        break;
    }

    switch (x)
    {
    case 'A':
        float getval;
        acceleration(&getval);
        *j = getval;
        return;
        break;
    }

    switch (x)
    {
    case 'm':
        float getval;
        mass(&getval);
        *j = getval;
        return;
        break;

    }

    switch (x)
    {
    case 'M':
        float getval;
        mass(&getval);
        *j = getval;
        return;
        break;
    }
    return;
}

void force(float *fma)                                      
{
    float acceleration, mass;

    printf("Enter a value for 'Mass', then 'Acceleration'.\n\n");
    scanf_s("%f\n%f\n", &mass, &acceleration, 2);

        *fma = mass * acceleration;

        return;

}

void acceleration(float *afm)
{                                                                                                                           //functions to take input from user and return float to varselect function
    float force, mass;

    printf("Enter a value for 'Force', then 'Mass'.\n\n");
    scanf_s("%f\n%f\n", &force, &mass, 1);

        *afm = force / mass;

    return;

}

void mass(float *fam)
{
    float force, acceleration;

    printf("Enter a value for 'Force', then 'Acceleration'.\n\n");
    scanf_s("%f\n%f\n", &force, &acceleration, 1);

    *fam = force / acceleration;

    return;
}

Answer 1

我认为这与您的代码无关...我可以说的是，如果您有一个 int 或 double 或 float 函数，它的工作方式与 void 相同。你输入你需要的参数，比如牛顿第二定律或任何你需要的参数。在那里你可以添加开关功能。切换后返回输出。 在其 {} 之后的 switch 之后，您放置返回输出或要返回的变量的名称。 要在控制台上获取它，您只需像这样： std::cout