Triadic @ (amend)

Applies a monadic verb to a certain value.

Syntax: .[x;y;z]

where z is a monadic verb to be applied and x is a structure to be indexed with y.

o)a:1 2 3; @[a;2;{x+1}]
1 2 4
o)d:`a`b`c!(1 2;3 4;5 6);
o)@[d;`a;{x+10}]
a| 11 12
b| 3 4
c| 5 6
o)t:flip `a`b!(!3;3+!3)
a b
---
0 3
1 4
2 5
o)@[t;`b;{x*3}]
a b
----
0 9
1 12
2 15
o)

For destructive updates use variable symbol in the first argument:

o)a:1 2 3; @[`a;2;{x+1}]
`a
o)a
1 2 4
o)