{if true then yes else no}
-> yes

{def switch
 {lambda {:n}
  {if {< :n 0}
   then :n is negative
   else {if {> :n 0}
   then :n is positive
   else :n is zero}}}}

{switch -12}
-> -12 is negative
{switch 12}
-> 12 is positive
{switch 0}
-> 0 is zero