current = current * 10 + (c - '0');

Question

I\'m trying to read unknown number of integers by this piece of code:

while (1) {
        int c = getchar ();
        if (c == EOF)
            break;
        el         


        

Answer 1

C specifies the 10 decimal digits, not surprisingly, as

0 1 2 3 4 5 6 7 8 9

C11 §5.2.1 further states "In both the source and execution basic character sets, the value of each character after 0 in the above list of decimal digits shall be one greater than the value of the previous.

Thus when assessing a string for characters that are digits, the language guarantees that subtracting '0' from a decimal digit char will result in its integer value.

if (isdigit (c))
  int value = c - '0';

This is not dependent on char using ASCII.