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cpointerscharoperators

What does the "++" operator do on a "char *"?

In the following function:

double dict(const char *str1, const char *str2) {

There is the following:

if (strlen(str1) != 0 && strlen(str2) != 0)
    while (prefix_length < 3 && equal(*str1++, *str2++)) prefix_length++;

What does the operator ++ do in *str1++ and *str2++?

Solution

  • The ++ operator in *str++ increments the pointer (not the thing pointed at).

    (*str)++;   /* Increment the character pointed at by str */
 *str++;    /* Increment the pointer in str */
*(str++);   /* Increment the pointer in str - the same, but verbose */

    There are two very different operations shown (one of them shown using two different but equivalent notations), though they both return the character that str pointed at before the increment occurs. This is a consequence of the precedence rules in the standard — postfix operators like ++ have higher precedence than unary (prefix) operators like * unless parentheses are used to alter this.