Reductions — sum, min, max & [OP]

Collapse a list to a single value with sum/min/max or the reduction metaoperator.

Reducing folds a list down to one value. Common reductions have named routines (sum, min, max), and any infix operator can reduce via the [ ] metaoperator.

The reduction metaoperator [OP] #

[+] inserts + between all the elements — [+] 1..5 is 1 + 2 + 3 + 4 + 5. Any associative infix works: [*] multiplies.

say [+] 1..5;
say [*] 1..5;

15
120

Named reductions #

sum, min, and max are the common ones as methods (or subs).

say (3, 7, 2, 9).max;
say (3, 7, 2, 9).min;
say (1..5).sum;

9
2
15

Notes #

• [+] () on an empty list returns the operator's identity — 0 for +, 1 for * — rather than failing.
• [<] reduces a comparison: [<] 1, 2, 3 is True (the list is strictly increasing), a neat use of chaining.
• For a custom fold, reduce takes the operator explicitly: (1..5).reduce(&infix:<+>) equals [+] 1..5.