Error message: subscript indices must be either positive integers or logicals

[preeti gaikwad]

Hello all, I am the new user or octave and would like to get help on this error message "subscript indices must be either positive integers or logicals"
I am using the function 

.....................................................................

for i=-10:1:10

z0 = (2/3)*lt*(1+R)/(1-R);

ze = (li/2)*log((1+(1/li)*z0)/(1-(1/li)*z0));

zp = ze;

A=(1-2*i)(L+2*ze)-2*(zp+lt);

B=(2*i+1)(L+2*ze);

Taui=li^2/D;

T=exp(-(x./Taui)).*(A.*exp([(-(A^2))/4*D.*x])-B*exp([(-B^2)/4*D.*x]));

 

end

F=T(1:nr);

.......................................................................where nr is the value of x 
and the value of D, li, lt are unknown and L and R is defined. I am using leasqr to call this function and fitted this function in my experimental results......All the time it is saying that A is not define and 
"subscript indices must be either positive integers or logicals"
the value of A has some problem I think but I am not getting what.....please help me for the same