Code-golf: generate pascal’s triangle

K (Wikipedia), 15 characters:

p:{x{+':x,0}\1}

Example output:

  p 10
(1
 1 1
 1 2 1
 1 3 3 1
 1 4 6 4 1
 1 5 10 10 5 1
 1 6 15 20 15 6 1
 1 7 21 35 35 21 7 1
 1 8 28 56 70 56 28 8 1
 1 9 36 84 126 126 84 36 9 1
 1 10 45 120 210 252 210 120 45 10 1)

It’s also easily explained:

p:{x {+':x,0} \ 1}
   ^ ^------^ ^ ^
   A    B     C D

• p is a function taking an implicit parameter x.

• p unfolds (C) an anonymous function (B) x times (A) starting at 1 (D).

• The anonymous function simply takes a list x, appends 0 and returns a result by adding (+) each adjacent pair (':) of values: so e.g. starting with (1 2 1), it’ll produce (1 2 1 0), add pairs (1 1+2 2+1 1+0), giving (1 3 3 1).

Update: Adapted to K4, which shaves off another two characters. For reference, here’s the original K3 version:

p:{x{+':0,x,0}\1}