Brainfuck interpreter in J

NB. Brainfuck interpreter
NB. Cells are arbitrary size, non-wrapping.
NB. Tape does not extend to the left.
tape =: 0x
ip =: 0
code =: '+-><'

fuck =: 3 : 0
tape =: (,[:x:0:)^:(ip&>:@#) tape
if. ',' = {.y do.
        tape =: ({.a.i.1!:1]1) ip} tape
elseif. '.' = {.y do.
        4 (1!:2)~ a.{~ip{tape
elseif. 2 > code i. {.y do.
        tape =: (>:`<: @. (code i. {.y) ip{tape) ip} tape
elseif. 4 > code i. {.y do.
        ip =: >:`<: @. (2-~code i. {.y) ip
elseif. '[' = {.y do.
        while. 0 ~: ip{tape do.
                fuck }. (#~ */\@:(+/\@:=&']' 0&>@- +/\@:=&'[')) y
        end.
end.
fuck^:(0:~:#) }. (#~ -.@(*/\)@:(+/\@:=&']' 0&>@- +/\@:=&'[')) y
)

NB. Cleans up tape and IP after execution,
NB. so that multiple programs can be ran in succession.

BF =: 3 : 0
fuck y
tape =: 0
ip =: 0
i.0             NB. Suppresses output (ip =: 0 would return 0, which would be printed)
)