for loop shape

[enemy]

Hello!
Please, what is the exact meaning of s[i] in the middle of the for loop?
Many thanks!

 //strlen function
//input: s= sequence of chars
//output: lenght of the sequence


int strlen(const char* s){
int i;
for (i=0,s[i]; i++);
return i
}

if we have char s[]="Happy New Year!";

strlen is of course 15;
and
"const char*s" is pointer (adress) of the first character in the sequence ,isn't it?

[Mats]

None of this code looks correct. =/

[Chervil]

Well, there are several careless errors in the code. If we first debug it and correct the errors, we get this code:

int strlen(const char* s)
{
    int i;
    for (i=0; s[i]; i++);
    return i;
}

the s[i] is the condition to be tested, just the same as in any other for loop.

The code is equivalent to:

int strlen(const char* s)
{
    int i = 0;
    while (s[i])
        i++;
    return i;
}

The loop will execute while the condition (s[i]) is true. This follows the normal rules, that a non-zero value is true and a value of zero is false. Hence the loop will execute until the zero byte is found which marks the end of the string.

[enemy]

Thanks, Chervil, finnaly clear!!!