% Horner's method 

% x [ a0 a1 ... ] 
/horner {
aload length              % x a0 a1 ... an n+1
dup 2 add -1 roll         % a0 a1 ... an n+1 x
exch 1 sub {              % a0 a1 ... P=an x 
  dup 4 1 roll            % a0 ... x ak P x
  mul add exch            % a0 ... a[k-1] P x
} repeat
% at end P(x) x on stack
pop                       % P 
} def