How to implement exponential function and log in HDL Coder?

i am trying to convert this matlab code to HDL verilog { xLow= double(5.0*(tonesLow-halfLow))/double(m); %Lower Sigmoid sLow = 1./(1+exp(-gamma*xLow));

tonesUp = m:1:255; xUp= double(5*(tonesUp-halfUp))/double((255-m)); %Upper Sigmoid sUp = 1./(1+exp(-gamma*xUp)); } i am getting problem in exp, like % function exp is not defined for value of class 'embedded.fi%