reduce.md

Reduce

Reducing is a general operation that can be performed on an array with the purpose of reducing or folding it into a single value (often a number but not always).

Reduce ( val0 arr len fun -- val )

Reduce takes an initial value val0, a pointer to an array and its length and a pointer to a function definition which takes two arguments and returns a single value.

It returns a single value.

:R\f!($%@\f@\G$2+)';

:R
\f!         \\ val0 arr len                     \f:fun
(           \\ val arr
$%@         \\ arr val arr[]
\f@ \G $    \\ val' arr                         where val' = f(val,arr[])
2+          \\ val' arr+2
)
'           \\ val
;

Count

:C'1+;

Count the numbers in an array.

> 0 [1 4 3 6 2] ?C R
5

Greatest

:G %%> \(')($ ') ;

Find the maximum number in an array.

> 0 [1 4 3 6 2] ?M R
6

Least

:L %%< \(')($ ') ;

Find the minimum number in an array.

> 1 [1 4 3 6 2] ?L R
1

Sum

:S+;

Sum of the numbers in an array.

> 0 [1 4 3 6 2] ?S R
16

Hash

:H1+^;

Hash of the numbers in an array.

> 0 [1 4 3 6 2] ?H R
7