Syntactic variation of a Fibonacci example

fib.c

// in reply to http://verse.systems/blog/post/2016-07-18-Software-Engineering-Teaching/

unsigned fibonacci(unsigned n) {
    unsigned a = 0, b = 1;
    unsigned sum = 0;
    for ( ; n > 0; --n) {
        unsigned t = b;
        b += a;
        a = t;
        sum += a;
    }
    return sum;
}