1) defining the Ycombinator
{def Y
 {lambda {:f :n}
  {:f :f :n}}}

2) defining non recursive functions
2.1) factorial
{def almost-fac
 {lambda {:f :n}
  {if {= :n 1}
   then 1
   else {* :n {:f :f {- :n 1}}}}}}

2.2) fibonacci
{def almost-fibo
 {lambda {:f :n}
  {if {<   :n 2}
   then 1
   else {+ {:f :f {- :n 1}} {:f :f {- :n 2}}}}}}

3) testing
{Y almost-fac 6}
-> 720
{Y almost-fibo 8}
-> 34

We could also forget the Ycombinator and names:

1) fac:
{{lambda {:f :n} {:f :f :n}}
 {lambda {:f :n}
  {if {= :n 1}
   then 1
   else {* :n {:f :f {- :n 1}}}}} 6}
-> 720

2) fibo:
{{lambda {:f :n} {:f :f :n}}
 {{lambda {:f :n}
  {if {<   :n 2} then 1
   else {+ {:f :f {- :n 1}} {:f :f {- :n 2}}}}}} 8}
-> 34