NB. B ! B ---------------------------------------------------------------

x=. ?100$2
y=. ?100$2
(x!y) -: (#.x,.y){1 1 0 1
(x!y) -: (z+x)!z+y   [ z=.{.0 4.5
(z!y) -: (($y)$z)!y  [ z=.?2
(x!z) -: x!($x)$z    [ z=.?2

(x!y) -: (40$"0 x)!y [ x=. ?10$2    [ y=. ?10 40$2
(x!y) -: x!40$"0 y   [ x=. ?10 40$2 [ y=. ?10$2

1 1 0 1 -: 0 0 1 1 ! 0 1 0 1


NB. B ! I ---------------------------------------------------------------

x=. ?100$2
y=. ?100$2e2
(x!y) -: (z+x)!z+y   [ z=.{.0 4.5
(z!y) -: (($y)$z)!y  [ z=.?2
(x!z) -: x!($x)$z    [ z=.?2e2

(x!y) -: (40$"0 x)!y [ x=. ?10$2    [ y=. +?10 40$2e2
(x!y) -: x!40$"0 y   [ x=. ?10 40$2 [ y=. +?10$2e2

1 1 0 1 -: 0 0 1 1 ! 0 1 0 1+4-4


NB. I ! B ---------------------------------------------------------------

x=. _1e2+?100$2e2
y=. ?100$2
(x!y) -: (z+x)!z+y   [ z=.{.0 4.5
(z!y) -: (($y)$z)!y  [ z=._1e2+?2e2
(x!z) -: x!($x)$z    [ z=.?2

(x!y) -: (40$"0 x)!y [ x=. _1e2+?10$2e2    [ y=. ?10 40$2
(x!y) -: x!40$"0 y   [ x=. _1e2+?10 40$2e2 [ y=. ?10$2

1 1 0 1 -: (0 0 1 1+3-3) ! 0 1 0 1


NB. I ! I ---------------------------------------------------------------

x=. _1e2+?100$2e2
y=. _1e2+?100$2e2
(x!y) -: (z+x)!z+y   [ z=.{.0 4.5
(z!y) -: (($y)$z)!y  [ z=._1e2+?2e2
(x!z) -: x!($x)$z    [ z=._1e2+?2e2

(x!y) -: (40$"0 x)!y [ x=. _1e2+?10$2e2    [ y=. _1e2+?10 40$2e2
(x!y) -: x!40$"0 y   [ x=. _1e2+?10 40$2e2 [ y=. _1e2+?10$2e2

1 1 0 1 -: (0 0 1 1+3-3) ! 0 1 0 1+3-3

'domain error' -: 1   ! etx 'chthonic'
'domain error' -: 0 0 ! etx ;:'sui generis'

4!:55 ;:'x y z'