Howard Wilson

How is one supposed to use the curl function in numeric mode? Tried with
syms r t p cs2 real; names=[r t p];
X=[r*sin(t)*cos(p);r*sin(t)*sin(p);r*cos(t)];% Basis of Covariant Vectors

bcov = [[ cos(t), -r*sin(t), 0], [ sin(t), r*cos(t), 0], [ 0, 0, 1]];
        
        
% Christoffel Symbols of the Second Kind

cs2 = zeros(3,3,3);
       
cs2(:,:,1) = [[ 0, 0, 0], [ 0, -r, 0], [ 0, 0, 0]];
 
cs2(:,:,2) = [[ 0, 1/r, 0], [ 1/r, 0, 0], [ 0, 0, 0]];
 
cs2(:,:,3) = [[ 0, 0, 0], [ 0, 0, 0], [ 0, 0, 0]];
 
curls([1, 2 ,3],names,bcovar,cs2,tn)

and gives

>> curltst
??? The following error occurred converting from sym to double:
Error using ==> sym.double at 25
DOUBLE cannot convert the input expression into a double array.
If the input expression contains a symbolic variable, use the VPA function instead.

Error in ==> curltst at 11
cs2(:,:,1) = [[ 0, 0, 0], [ 0, -r, 0], [ 0, 0, 0]];

Appropriate book for Mech and Matlab.