在while循环中使用scanf（）。 在％不起作用之前放一个空格

Question

double bet = 0;
do
      {
        printf("How much would you like to bet? The minimum bet is $5.00: ");
        scanf(" %.2lf",&bet);
      } while (bet < 5);

My scanf just takes value once and goes into infinite loop. I have read many posts, and found the general way to solve this is put a space before %. I did this, but the problem still exists. Say it first read bet = 4, and it is supposed to ask me to enter a number again, but it just keeps printing "How much would you like to bet? The minimum bet is $5.00: ". Why is that?

Answer 1

The problem is your scanf format string. Your compiler might have warned about it. The . isn't allowed. As a result, the scanf call is returning 0 and is not consuming any characters.

Try changing it to this:

double bet = 0;
do {
    printf("How much would you like to bet? The minimum bet is $5.00: ");
    scanf(" %lf", &bet);
} while (bet < 5);

It would also be a good idea to check the return value from scanf . It should return the number of values successfully decoded.

Answer 2

Is .2 is required in your code. It is showing warning as a use of . in the code. Try removing it. Then it is working fine. ie use only %lf