// "109.hac" -- should pass
// copy-modified from "039.hac"

// note: L2 has no direction specified, so may be send or receive, or both!
defproc sum_diff(chan?(int) L1, L2; chan!(int) R) {
int x, z, w;
chan(int) M;
chp {
	{L1#(x); L1?}, {L2#(z); L2?};
	M!(x-z)
}
chp {
	M?(w);
	R!(w)
}
}

