I made a code for calculating DFT of any signal. I tested it with many functions but when I introduced a complex sine, my DFT give a "unilateral signal". I've never seen something like that. Is it OK? I supposed to get a bilateral DFT ($-f$ and $+f$).
Complex sine: $$\exp(i\cdot2\cdot\pi\cdot2.5/128\cdot t)$$
My DFT plot:
Is it OK? What does it mean?