problem representing a shape using several spectral elements in IFFT

Hello ,i have a step function described by the following code.

i have tried to represent the shape using ifft by 8 elements.

but when i i do fft using those 8 elements i am not getting backs something even close to the original shape(i get straight zero line ).

where did i go wrong?

Thanks .

function y=unitstep(t)
  y=(t>=0)
end

t=linspace(-1,1,1000);
y=-unitstep(t-0.5)+unitstep(t+0.5);
z=ifft(y,16);
h=ftt(z);
plot(h);