chrispsn

    (Π):!/:  / make table
    
    Π[`a   `b
     ( 1    2
       3    4)]

  {$[2>#?x;x;,/o'x@&'~:\x<*1?x]}    / Quicksort
  
  (+':,)\~!10                       / Pascal's triangle
  
  {x x}{x{x[x]y}y}                  / Y-combinator