gah

wanted: simple c primality test

prime?() should return 0 if composite and 1 if prime -- I'm trying to plot this:

x_(n+1)=cos(y_(n) + 2( prime?(floor(128 * (sin ((e^(x_(n)) - (e^(y_n))))-1);
y_(n+1)=sin(x_(n) + 2( prime?(floor(128 * (sin ((e^(y_(n)) - (e^(x_n))))-1);