CODEWITHSUNDEEP
cinputkey-value
mintbox
mintbox

Reputation: 167

c : How to signal end of input

in this simple program that prompts users to input a polynomial,

I used int 999 as a value that represents end of input.

However, this is not a good design because users will not be able to input a polynomial node with a coeff of 999.

Is there an alternative key that can be unique to represent end of input?

Relevant Code : 

int coeff;
int expon;
int i = 1;

printf("\nInput for polyNode %d  (999 for exit):",i);
printf("\n\tInput coeff : ");
scanf("%d",&coeff);

while(coeff != 999)
{
    printf("\tInput expon : ");
    scanf("%d",&expon);
    insertBack(&polynomial, &polynomialRear, coeff, expon);

    i++;
    printf("\nInput for polyNode %d  (EOF for exit):",i);
    printf("\n\tInput coeff : ");
    scanf("%d",&coeff);
}

printPoly(polynomial);
printf("\n");

Upvotes: 3

Views: 3346

Answers (2)

user3121023
user3121023

Reputation: 8286

You can check the return of scanf. If the scan is successful it will, in this case, return 1 for one item scanned. If the scan is unsuccessful, it will return either 0 or EOF. Input of any non-integer value (letters...) will end the while ( 1) loop.
Then clear the input stream with getchar() in a while loop.

int coeff;
int expon;
int i = 1;

while(1)
{
    printf("\nInput for polyNode %d :",i);
    printf("\n\tInput coeff : ");
    if ( ( scanf("%d",&coeff)) != 1) {
        break;
    }

    printf("\tInput expon : ");
    if ( ( scanf("%d",&expon)) != 1) {
        break;
    }

    insertBack(&polynomial, &polynomialRear, coeff, expon);

    i++;
}
while ( ( i = getchar ()) != '\n' && i != EOF) ;//clear input stream

printPoly(polynomial);
printf("\n");

Upvotes: 1

Vladimir T
Vladimir T

Reputation: 866

You can wait till end character will arrive, it maybe any symbol you wish (not a number, CRLF, TAB etc). After receiving of a complete input string do a processing.

Upvotes: 0

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