need code to check if the value is numeric in C

[Mikerush7]

I am student, taking C programming now. I have assignment to write function to check if inputed data is numbers. if not - it should write that, and ask to enter number again. I wrote code, to write error message, but dont know how to make program to work on next input.. should I call the Main function again ? int main() { double hours; //hours worked in a week double payrate; // hourly salary double grosspay; //total weekly payment int k; //number of values read printf ("Enter number of hours, and hourly pay (or press 0 to exit) \n"); while ((k = scanf ("%lf%lf", &hours, &payrate))==2) { if (isdigit(hours) !=0) return hours; else printf ("You entered invalid data, please enter number of hours \n"); if (isdigit(payrate) !=0) return payrate; else printf ("You entered invalid data, please enter payrate \n"); if (hours==0 || payrate==0) { printf ("Good Bye. \n\n"); system("PAUSE"); return 0; } double grosspay; grosspay = calculateGrossPay(hours, payrate); printf ("Hours worked: %.2f\n", hours); printf ("Hourly Rate: %.2f\n\n", payrate); printf ("Your weekly payment is: $ %.2f \n\n\n", grosspay);

[Lost User]

You cannot use a double parameter as input to the isdigit()[^] function. You should read your numbers in as strings and then apply isdigit() to each character, using a loop. Rather than having all your code in the main() function, you may want to think about writing a helper function that will input the string, validate it and return the converted value.

One of these days I'm going to think of a really clever signature.

[Mikerush7]

i dont really know how to do that yet... Ok, i will try.. is there a general format of that function somewhere?

[Lost User]

Mikerush7 wrote:

is there a general format of that function somewhere?

Assuming you mean isdigit(), I put the link in my previous message.

One of these days I'm going to think of a really clever signature.

[CPallini]

Mikerush7 wrote:

while ((k = scanf ("%lf%lf", &hours, &payrate))==2)

If scanf succeeds then you need no other check.

Mikerush7 wrote:

should I call the Main function again

No. You may call scanf (if you are allowed to use it) many times inside your main function.

Veni, vidi, vici.

[David Crow]

Mikerush7 wrote:

while ((k = scanf ("%lf%lf", &hours, &payrate))==2)

Without a full understanding of assignments and expressions, mixing the two in one statement is highly discouraged.

Mikerush7 wrote:

return hours;

While I'm not sure who you'd be returning hours worked to or why, the compiler should have at least warned you about loss of data.

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[Lost User]

DavidCrow wrote:

the compiler should have at least warned you

Given the number of syntax errors elsewhere I don't think a compiler has ever seen this sample.

One of these days I'm going to think of a really clever signature.

[Mikerush7]

thank you everybody for help. I will keep working on it. my teacher is not helping, so I am on my own..

[C Mahesh]

Build your logic based on the following example. int main( ) { char n ; int no = 0 ; printf("Enter a no " ); while( (n = (char)getche( )) != '\r') //Check for enter key { if( n >= '0' && n <= '9' ) { n = n - 48 ; no = (no * 10) + n ; } else{ printf("\nInvalid. "); } } printf("\n %d " , no ) ; return 0 ; }