Indexing is effected using the verb { (from), and indexed replacement using the adverb } (amend). From and amend are symmetric. These are described in entries in the Dictionary.
From and amend provide all the functionality of bracket indexing found in other languages, and much more.
Examples of from
]m=. 4 5$'cabletreatbraidrider' cable treat braid rider
pick row 2:
2{m
braidpick columns 1 2:
1 2{"1 m
ab
re
ra
idpick the element in row 2, column 1:
(<2 1){m
rscattered indexing:
(0 3;2 2;2 3;3 0){m
lair
Examples of amend
replace row 2:
'godel' 2 } m cable treat godel rider
replace columns 1 and 2:
('xyzt',.'XYZT') 1 2}"1 m
cxXle
tyYat
bzZid
rtTerreplace element in row 2, column 1:
'Z' (<2 1)}m cable treat bZaid rider
scattered replacement:
'ABCD' (0 3;2 2;2 3;3 0)}m cabAe treat brBCd Dider