Fgets（）需要輸入在讀到字符數組後輸入兩次

Question

當我輸入任何東西評估爲假在函數isFloat(char array[])我需要點擊輸入兩次，以保持程序運行。

如果我註釋掉一切，但fget()命令一切要求我輸入兩次。什麼可能導致這個？我正在沖洗stdin，\n被strtok()刪除。 printf()函數是否會導致問題？我讀過scanf()和fgets()一起使用會導致問題。但在這裏他們沒有。

問題區域

printf("first number: "); 
    fgets(input, TEN_THOUSAND, stdin); 
    strtok(input, "\n"); 
    success = isFloat(input); 
    if(success) 
     firstNum = atof(input); 

全碼：

#include<stdio.h> 
#include<stdlib.h> 
#include<stdio.h> 
#include<string.h> 

int isFloat(char array[]) 
{ 

int m = 0; 
int periodCount = 0; 

for(m=0; array[m] != '\000'; m++) 
    { 
     if(array[m] == '1' || array[m] == '2' || array[m] == '3' || array[m] == '4' || array[m] == '5' || array[m] == '6' || array[m] == '7' || array[m] == '8' || array[m] == '9' || array[m] == '0') 
      { 
      } 
     else 
      { 
       if(array[m] == '.' && periodCount == 0 && m != 0 && m+1 != '\n') 
        periodCount = 1; 
       else 
        return 0; 
      } 
    } 
return 1; 
} 

void eatLine() 
{ 
    while (getchar() != '\n'); 
} 

int main() 
{ 

double firstNum = 0.0; 
double secondNum = 0.0; 
double totalNum = 0.0; 
int success = 0; 
int TEN_THOUSAND = 10000; 
char input[TEN_THOUSAND]; 

//Outputs assignment header 
printf("CS201 - Lab 2 - Number Adder\n\n"); 

printf("first number: "); 
fgets(input, TEN_THOUSAND, stdin); 
strtok(input, "\n"); 
success = isFloat(input); 
if(success) 
    firstNum = atof(input); 

while(!success) 
{ 
    eatLine(); 
    //The one is for testing purposes 
    printf("-- bad input --\n"); 
    printf("first number: "); 
    fgets(input, TEN_THOUSAND, stdin); 
    strtok(input, "\n"); 
    success = isFloat(input); 
    if(success) 
     firstNum = atof(input); 
} 

printf("second number: "); 
fgets(input, TEN_THOUSAND, stdin); 
strtok(input, "\n"); 
success = isFloat(input); 
if(success) 
    secondNum = atof(input); 

while(!success) 
{ 
    eatLine(); 
    //The one is for testing purposes 
    printf("-- bad input --\n"); 
    printf("second number: "); 
    fgets(input, TEN_THOUSAND, stdin); 
    strtok(input, "\n"); 
    success = isFloat(input); 
    if(success) 
     secondNum = atof(input); 
} 

//adds the numbers 
totalNum = firstNum + secondNum; 

//Solves ugly formatting problem by firstly including a newline 
//after the input is garnered. then it outputs firstNum and totalNum 
//in a field of 11 spaces with a newline terminator. This decrements 
//11 to 10 on the secondNum line to compensate for the space that the + takes up. 
printf("\n%11.2f\n", firstNum); 
printf("%s%10.2f\n", "+", secondNum); 
printf("-----------\n"); 
printf("%11.2f\n\n", totalNum); 

return 0; 
} 

Answer 1

當我輸入任何內容，其值在功能isFloat(char array[])我需要鍵入回車兩次，以保持假程序運行。

這是因爲您有一行代碼需要輸入一行文本。

while(!success) 
{ 
    eatLine(); // Culprit