In Curve: Added numerical FD differentiation if derivative is not supplied. Added arc length computation based on the derivative. Added arc length parameterization (but this function is very slow.). In +util: Added fzero_vec.m and integral_vec.m, which call fzero and integral but take vector arguments.

function printExpr(expr)
    result = evalin('caller',expr);
    fprintf('%s => %s\n', expr, toString(result));
end