Question

Possible Duplicate:
In C arrays why is this true? a[5] == 5[a]

In a C++ reference book, I found an example that accessed a string like following:

void main()
{
    char *str = "Test";
    int len, i;

    clrscr();

    len = strlen(str);
    for(i=0 ; i<len ; i++)
    {
        printf("%c", i[str]);
    }

    getch();
}

Why does i[str] work? i is a variable, not an array.

It also works if the string is declared as str[] instead of *str.

Answer 1

Char pointers point to the memory location at the start of a string, and the array indexes (eg, str[i]) are basically adding i iterations to the start of the string.

So, str + i = str[i] = i[str] = i + str

Using this inside printf, like you are doing, all of these will evaluate the same:

printf("%c", str[i]);
printf("%c", i[str]);
printf("%c", *(str+i));
printf("%c", *(i+str));

See also: With arrays, why is it the case that a[5] == 5[a]?