fold
(Redirected from Over)
Fold
f/y
x f/y
x f/y
fold, also known as reduce, foldl and over, takes a dyadic function f and reduces an array y using it.
Fold is a very strong utility. For example, you can sum a list using +/.
+/1 2 3 4
10
,/("ab";1;`d`a`b)
("a"
"b"
1
`d
`a
`b)
Specifying a left argument x uses it as an initial value.
3 +/1 2 3 4 13
When used with functions that take more than 2 arguments, fold can take multiple arguments, of which the first one is always the initial value.
{x,y,z}/["A";1 2 3;"BCD"]
("A";1;"B";2;"C";3;"D")