Conway's Game of Life in Q:
life:{3=a-x*4=a:2(sum -1 0 1 rotate\:,’/)/x} life:{3=a-x*4=a:2(sum -1 0 1 rotate\:,’/)/x} life←{↑1 ⍵∨.∧3 4=+/,¯1 0 1∘.⊖¯1 0 1∘.⌽⊂⍵} life←{≢⍸⍵}⌺3 3∊¨3+0,¨⊢