ITEM AMEND (_) u}y is an amendment of the items of y whose shape is the shape of an item of y. Each atom is selected as a corresponding atom in an item, the item being specified by the index in the corresponding position of u i.# y (whose shape must be the shape of an item of y). Thus:
m=.0 1 3 1 2
u=. m&{
y u i.}.$y
abcde 0 1 3 1 2
fghij
klmno
pqrst
u}y m}y
agrio agrio
AMEND (_ _) If x has the same shape as the index array j=. u i.$y, then x u} y amends x and y by inserting the atoms of x in the selected positions of y. More generally, the shape of x may be a suffix of the shape of j, and the result is an amendment of ($j) $ ,x and y. Thus, 'BD'1 3} 'abcd' is aBcD, and if x=.'AGMS' and
u=.(<0 1)&|: (the diagonal verb), then u i.$y is 0 6 12 18, and: