/compose { % f g -> { g f }
  [ 3 1 roll exch
  % procedures are not executed when encountered directly
  % insert an 'exec' after procedures, but not after operators
  1 index type /operatortype ne { /exec cvx exch } if
  dup type /operatortype ne { /exec cvx } if
  ] cvx
} def

/square { dup mul } def
/plus1  { 1 add } def
/sqPlus1 /square load /plus1 load compose def