`reduce` for filters

Aggregate a list (starting from the left) to a single value using an accumulator closure.

Signature

> reduce {flags} (closure)

Flags

--fold, -f {any}: reduce with initial value

Parameters

closure: Reducing function.

Input/output types:

input	output
list<any>	any
table	any
range	any

Examples

Sum values of a list (same as 'math sum')

> [ 1 2 3 4 ] | reduce {|it, acc| $it + $acc }
10

reduce accumulates value from left to right, equivalent to (((1 - 2) - 3) - 4).

> [ 1 2 3 4 ] | reduce {|it, acc| $acc - $it }
-8

Sum values of a list, plus their indexes

> [ 8 7 6 ] | enumerate | reduce --fold 0 {|it, acc| $acc + $it.item + $it.index }
24

Sum values with a starting value (fold)

> [ 1 2 3 4 ] | reduce --fold 10 {|it, acc| $acc + $it }
20

Iteratively perform string replace (from left to right): 'foobar' -> 'bazbar' -> 'quuxbar'

> [[foo baz] [baz quux]] | reduce --fold "foobar" {|it, acc| $acc | str replace $it.0 $it.1}
quuxbar

Replace selected characters in a string with 'X'

> [ i o t ] | reduce --fold "Arthur, King of the Britons" {|it, acc| $acc | str replace --all $it "X" }
ArXhur, KXng Xf Xhe BrXXXns

Add ascending numbers to each of the filenames, and join with semicolons.

> ['foo.gz', 'bar.gz', 'baz.gz'] | enumerate | reduce --fold '' {|str all| $"($all)(if $str.index != 0 {'; '})($str.index + 1)-($str.item)" }
1-foo.gz; 2-bar.gz; 3-baz.gz

Concatenate a string with itself, using a range to determine the number of times.

> let s = "Str"; 0..2 | reduce --fold '' {|it, acc| $acc + $s}
StrStrStr

Merge multiple records together, making use of the fact that the accumulated value is also supplied as pipeline input to the closure.