Question

/* this is just a function I'm trying to make for a bigger program that calcs the area of a room. When the answer <= 0 I want to get the function to take over, but I keep getting to few arguments error when I compile it. Any help will be gladly appreciated.*/

#include <stdio.h>
int validInput(double len);
int main(void)
{
double len ;
int check;
printf("\nEnter length of room in feet:");
        scanf("%lf", &len);
check = validInput();

return 0;

}

int validInput(double len)
{
int check;
if (len <= 0 )
printf("\nNumbers entered must be positive.");
return check;
}

Answer 1

First... you didn't pass any value to validInput(). I guess your code here above won't even compile...

You should change this line:

check = validInput();

to:

check = validInput(len);

Also consider that variable "check" returned by your function is neither initialised nor set...

P.S. please indent your code...

Answer 2

这一行：

check = validInput();

缺少参数。建议：

check = validInput( len );

当然，代码应该从调用scanf()检查返回值而不是参数值，以确保操作成功。在这种情况下，返回值应为1.任何其他返回值都表示发生了错误。

关于validInput()函数：

变量check永远不会初始化为任何特定值。建议：

int validInput(double len)
{
    int check = 1; // indicate valid

    if (len <= 0 )
    {
        check = 0; // indicate not valid
        printf("\nNumbers entered must be positive.\n");
    }

    return check;
}

注意：调用\n时的尾随printf()是强制立即输出文本而不是在内部stdout缓冲区中设置，直到程序退出，此时它会输出。

将适当的错误检查纳入main()函数会导致：

#include <stdio.h>   // scanf(), printf()
#include <stdlib.h>  // exit(), EXIT_FAILURE

int validInput(double len);

int main(void)
{
    double len ;
    int check;

    printf("\nEnter length of room in feet:");
    if( 1 != scanf("%lf", &len) )
    { // then scanf failed
        perror( "scanf for length of room, in feet, failed" );
        exit( EXIT_FAILURE );
    }

    // implied else, scanf successful

    check = validInput( len );

    printf( "the user input was %s\n", (check)? "valid" : "not valid");

    return 0;

} // end function: main

Making a validation function to tell if the number entered is positve

2 个答案: