HEAD (_) {.y selects the leading item of y; that is, y if y is an atom, and 0{y if not.
TAKE (1 _) If x is an atom, x{.y takes from y an interval of |x items; beginning at the front if x>:0, ending at the tail if x<0:
y 2{.y 4{.y _4{.y
0 1 0 1 0 1 0 0
2 3 2 3 2 3 0 1
4 5 4 5 2 3
0 0 4 5
In an overtake (as in 4{.y and _4{y above), extra items consist of fills; zeros if y is numeric, boxed empties if it is boxed, and spaces otherwise. If y is an atom, the result of 1{.y is a one-element list. Finally, if $y is 0,s, then the fill items are s$0 or s$<'' or s$' '.
In general, x may be a list of length not more than $$y; the effect of element k is (k{x){."(($$y)ΓÇôk) y.
