似乎无法在 function 和 main 之间传递信息

Question

我无法让我的代码正常运行。在这里:

#include <stdio.h>

void intro_msg( ); 
float compass_value( );
float direction(  );

int  main ( void )
{

  float compass;

  intro_msg( ) ;

  compass_value(compass );

  direction(compass );

  return ( 0 ) ;

}  

void intro_msg(void)
{
   printf("Welcome to the Compass Program \n \n");
}

float compass_value(compass )
{
   printf("Please enter a value for the compass direction. (0 - 360 degress ) :  ");
   scanf("%f", &compass);
   printf("You entered %f degrees \n" , compass);
   return(compass);
}


float direction(compass)
{
   if (compass >= 354.38 && compass <= 360.00){
      printf("You are heading North \n");
  }
   else if (compass >= 0.0 && compass <= 39.37){
      printf("You are heading North \n");
  }
   else if (compass >= 39.38 && compass <= 84.37){
      printf("You are heading Northeast \n");
  }
   else if (compass >= 84.38 && compass <= 129.37){
      printf("You are heading East \n");
  }
   else if (compass >= 129.38 && compass <= 174.37){
      printf("You are heading Southeast \n");
  }
   else if (compass >= 174.38 && compass <= 219.37){
      printf("You are heading South \n");
  }
   else if (compass >= 219.38 && compass <= 264.37){
      printf("You are heading Southwest \n");
  }
   else if (compass >= 264.38 && compass <= 309.37){
      printf("You are heading West \n");
  }
   else if (compass >= 309.38 && compass <= 354.37){
      printf("You are heading Northwest \n");
  }
   else 
   {
      printf("You did not enter a value between 0 - 360 degrees");
   }
}

我正在尝试从用户那里获得 0 - 360 度之间的度数，记录下来，然后确定他们面对的方向(北、南、东北等)，但我的罗盘值从未被记录。

在向用户询问值后，我立即去打印值并得到 0.0，而不是用户输入的值。我在这里做错了什么？

Answer 1

我想您知道您实际上是按值将 compass 变量传递给 compass_value()。意味着更改不会反射(reflect)到主函数的罗盘变量中。

我看到您正在返回读取值，但您在调用主函数中的 compass_value() 时没有将其接收到任何内容。尝试接收它:

compass = compass_value(compass);