:: ********** 11. num-leaves **********
|=  a=*
^-  @ud
?~  a
  1
?@  a
  1
(add $(a -:a) $(a +:a))

:: ********** 12. noun-to-list **********
|=  a=*
=/  lis=(list @)  ~
^-  (list @)
|-
?@  a
  (flop [a lis])
?@  -.a
  $(lis [-.a lis], a +.a)
$(a [-<.a [->.a +.a]])

:: ********** 13. samefringe **********
|=  [m=* n=*]
^-  @f
?:  =(m n)
  %.y
?@  m
  ?@  n
    ?:  =(m n)
      %.y
    %.n
  %.n
?@  n
  %.n
?@  -.m
  ?@  -.n
    ?:  =(-.m -.n)
      $(m +.m, n +.n)
    %.n
  $(m m, n [-<.n [->.n +.n]])
?@  -.n
  $(m [-<.m [->.m +.m]], n n)
$(m [-<.m [->.m +.m]], n [-<.n [->.n +.n]])

:: ********** 14. insertion-sort **********
|%
++  insert
|=  [sorted=(list @) to-insert=@]
|-  ^-  (list @)
?~  sorted
  [to-insert ~]
?:  (lte to-insert i.sorted)
  [to-insert sorted]
[i.sorted $(sorted [t.sorted])]
--
:-  %say
|=  [^ [to-sort=(list @) ~] ~]
:-  %noun
=/  sorted=(list @)  ~
|-  ^-  (list @)
?~  to-sort
  sorted
?~  sorted
  $(sorted [i.to-sort sorted], to-sort t.to-sort)
?:  (lth i.to-sort i.sorted)
  $(sorted [i.to-sort sorted], to-sort t.to-sort)
$(sorted (insert sorted i.to-sort), to-sort t.to-sort)