reduce for filters

Aggregate a list 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:

inputoutput
list<any>any
rangeany
tableany

Examples

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

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

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

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