(pattern *) pat & pattern * pat

what is the difference between 1 & 2?

1. pat = (PATTERN *)
vector(1,(int)*num_patfiles,sizeof(PATTERN));

2. pat = PATTERN * vector(1,(int)*num_patfiles,sizeof(PATTERN));

look at it this way

vector(1,(int)*num_patfiles,sizeof(PATTERN));

this returns something. My guess is a pointer of some sort.

(PATTERN *)

this is a cast.So putting the 2 together you are casting the result of vector(blahblah) to a PATTERN* or a pointer to a PATTERN and storing that in the variable pat.

pat = PATTERN * vector(1,(int)*num_patfiles,sizeof(PATTERN));

This on the other hand is a multiplication. It shouldn't compile as pointers cant be multiplied. This says multiply PATTERN with the result of vector(blahblah) and store the result in pat.