Structure usage from Dennis Ritchie's manual

Below is a copy pasted code from Dennis Ritchie's manual and is regarding the definition of the printf statement. The part what I havent understood throughout this program is usage of 'charpp' and 'doublep' elements of nameless structures in conjunction with an integer pointer 'ap'. Is that even valid?

Code:

---

printf ( fmt, args )
char fmt [ ] ;
{
      char *s;
      struct { char **charpp ; };
      struct { double *doublep ; };
      int *ap, x, c ;
    ap = &args ; /* argument pointer */
    for ( ; ; ) {
        while ( ( c = *fmt++ ) != ´%´ ) {
            if(c == ´\0´ )
                return ;
            putchar(c);
        }
        switch ( c = *fmt++) {
        /* decimal */
        case ´d ´:
            x = *ap++ ;
            if(x < 0) {
                x = -x;
                if ( x<0 ) { /* is - infinity
                printf ( "-32768" ) ;
                continue ;
                }
            putchar ( ´-´);
            }
            printd(x);
            continue ;
        /* octal */
        case ´o´:
            printo ( *ap++);
            continue ;
        /* float, double */
        case ´f ´:
            /* let ftoa do the real work */
            ftoa ( *ap.doublep++);
            continue ;
        /* character */
        case ´c´:
            putchar ( *ap++);
            continue ;
        /* string */
        case ´s´:
            s = *ap.charpp++ ;
            while ( c = *s++ )
            putchar(c);
            continue ;
        }
        putchar(c);
    }
}

/**
Print n in decimal ; n must be nonnegative
*/

printd(n)
{
    int a ;
    if ( a=n/10 )
    printd(a);
    putchar ( n%10 + ´0´ ) ;
}

/**
Print n in octal, with exactly 1 leading 0
*/

printo(n)
{
    if (n)
    printo ( ( n>>3 ) &017777 ) ;
    putchar ( ( n&07 ) +´0´ ) ;
}

---

Thanks
Pallavi

from your code, i guess you are looking at the Bell Labs online c programming reference manual? if so, you are looking at a description of a really early version of C that allowed all sorts of things that are no longer valid. so the answer is no, that is not valid in ANSI C or even most older C implementations.