Depending on whether you want high speed or high accuracy, you may prefer
float(rectform(expr)) -- almost always higher accuracy (sometimes much
higher)
ev(rectform(exp),float:true,numer:true) -- almost always higher speed
(sometimes much faster)
The difference is only significant for large or numerically unstable
expressions. In the first case, the rectform is first calculated
symbolically, then evaluated numerically. In the second case, the rectform
works directly with the floating form.
(C1) qq:expand((x-1)^100)$
(C2) float(rectform(qq)),x=3D1/2+%i;
Evaluation took 1.43 seconds
(D2) 48224.97071876014 %I - 50827.60730619192
(C3) rectform(qq),float,x=3D1/2+%i;
Evaluation took 0.80 seconds
(D3) - 1.799013031517631E+22 %I - 4.487393810975757E+21