Popr

module num:

imports:
  module stack
  module control

__ max of two values
max: [] ap20 dup . dup tail | [<= !] . popr nip

__ min of two values
min: [] ap20 dup . dup tail | [> !] . popr nip

__ is argument odd?
odd: 1 &b 1 ==

even: 1 &b 0 ==

bound: [dup_under >= !] dip21 dup_under <= !

up_to: 0 swap bound

module list:

imports:
  module control
  module stack
  module logic

__ take rightmost value from quote
head: popr nip
top: dup head

__ return the length of a list
length:
  [0 swap] pushl
    [[[1+] [tail] para] .]
    [popr popr valid]
    iterate tail head