Question

我有一个计算器可以减少分子的质量，并希望用if函数调用它。这是我目前的代码：

int program ();
int main()
{
    printf("Press 1 to calculate the reduced mass of a molecule or press any other button to exit:");
    scanf ("%lg",&repeat);

    if(repeat==1)
    {
    program();
    }
    else
    {
    return(0);
    }
}

int program ()
//etc...

我对C不太熟悉，所以解释可能有用。这也是为了让你可以多次重复这个功能吗？

Answer 1

如果从C开始，可以先使用程序（已编译的C）参数。通过这种方式，您可以为程序提供 N 多次调用program()函数。

E.g。

   // Includes that have some library functions declarations
   #include <stdio.h>
   #include <stdlib.h>

   // argc and argc can be provided to the main function.
   // argv is an array of pointers to the arguments strings (starting from 0)
   int main(int argc, char *argv[]) {
      if (argc < 2) return 1; // argc number of parameters including the program name itself
      int repeat = atoi(argv[1]); // atoi convert a string to integer

      // repeat-- decrements repeat after its value was tested against 0 in the while
      while (repeat-- > 0) {
         program();
      }

      return 0;
   }

argc 针对2进行测试，因为程序名称本身是第一个参数，您需要至少2个，使用N. E.g。

   ./myprog 5

将运行 program（） 5次。

Answer 2

I'm not too experienced with C, so an explanation might be useful.
不确定你究竟需要解释：

int program (); <-- function prototype for "program" defined here so you can call it in
int main()      <--  main. 
{
    // Display a message
    printf("Press 1 to calculate the reduced mass of a molecule or press any other button to exit:");
    // store the value typed by the user as a double, also it will accept scientific 
    // notation (that’s he g part). So you could enter 3.964e+2 if you wanted... an 
    // int or even a char would have been fine here
    scanf ("%lg",&repeat);

Also would this make it so that you can repeat the function as many times as you like? 不，那不是。首先，它不会编译，因为没有“重复”的定义;第二，你错过了一个循环机制。 for，while，do/while，递归......不管它是什么。您的代码可以很容易地通过无限循环完成：

int main()
{
    double repeat = 0;
    for(;;) {
        printf("Press 1 to calculate the reduced mass of a molecule or press any other button to exit:");
        scanf ("%lg",&repeat);

        if(repeat==1)
        {
            program();
        }
        else
        {
            return(0);
        }
    }
}

在C中调用带有if语句的函数

2 个答案: