Question about sin/cos CORDIC algorithm

[leemango1998]

Hi, I have a question about CORDIC algorithm in liquid-fpm. According to wiki, the basic operations in rotation in CORDIC are showed below:

 x[i+1] = x[i] - d[i] * y[i] * 2^(-i)
 y[i+1] = y[i] + d[i] * x[i] * 2^(-i)
 θ[i+1] = θ[i] − d[i] * α[i]

where d[i] is either 1 or -1. I note that in liquid-fpm, we use XOR operation to deal with the judgment of positive and negative signs.

liquid-fpm/src/sincos.cordic.c

Lines 119 to 128 in a8ff545

	for (i=0; i<n; i++) {
	d = ( z>=0 ) ? 0 : -1;
	// d = z >> 31;
	tx = x - ((y>>i)^d)-d;
	ty = y + ((x>>i)^d)-d;
	tz = z - ((Q(_cordic_Ak_tab)[i]^d)-d);
	x = tx;
	y = ty;
	z = tz;

But I suspect there is a bug in the above code. In line 123, there seems to be a missing parenthesis of ((y>>i)^d) -d;. They should be a whole like line 125.

liquid-fpm/src/sincos.cordic.c

Line 125 in a8ff545

tz = z - ((Q(_cordic_Ak_tab)[i]^d)-d);

Is there a trick here that I don't know about or is this a simple clerical error? Looking forward to your reply.