[Gretl-users] limitations of maximum likelihood estimations

Hi What are the limitations in the format for the formulas of log-likelihood ? I tried unsuccessfully to make a mle with the following script: genr BUY = BUYE + BUYF genr SELL = SELLE + SELLF genr c1 = 0.5 genr c2 = 0.2 genr c3 = 0.2 mle loglik= log (c3*((1-c1)*((0.5*(1+c2))^BUY *(0.5*(1-c2))^SELL)+ c1*((0.5*(1-c2))^BUY *(0.5*(1+c2))^SELL)) +(1-c3)*0.5^BUY*0.5^SELL) params c1 c2 c3 end mle Can you see why ? Thanks