I was wondering if someone could help clarify the calculate function on pset5 speller.c (I've copied it below). I'm mostly having difficulty understanding what "->" is exactly doing. Thanks!

double calculate(const struct rusage* b, const struct rusage* a) 
    if (b == NULL || a == NULL) 
        return 0.0; 
    { return ((((a->ru_utime.tv_sec * 1000000 + a->ru_utime.tv_usec) -
         (b->ru_utime.tv_sec * 1000000 + b->ru_utime.tv_usec)) +
         ((a->ru_stime.tv_sec * 1000000 + a->ru_stime.tv_usec) -
         (b->ru_stime.tv_sec * 1000000 + b->ru_stime.tv_usec))) / 1000000.0); 

Both a and b are pointers to structures. The -> is not so much an operator as a selector. It allows you to select a specific element from the structure, as in a->ru_utime.tv_sec BTW, the dot in the middle serves a similar function.

These are topics that you will see in later psets, so I'll leave the explanation to Prof. Malan's lectures.

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