gno.land/p/moul/fp

Functional helpers over []any: the map / filter / reduce set, plus the grouping and zipping pieces that usually get rewritten inline.

1numbers := []any{1, 2, 3, 4, 5, 6}
2
3isEven := func(v any) bool { return v.(int)%2 == 0 }
4double := func(v any) any  { return v.(int) * 2 }
5sum    := func(a, b any) any { return a.(int) + b.(int) }
6
7evens  := fp.Filter(numbers, isEven)   // [2 4 6]
8bigger := fp.Map(evens, double)        // [4 8 12]
9total  := fp.Reduce(bigger, sum, 0)    // 24

The set

Three named function types keep signatures readable: Mapper func(any) any, Predicate func(any) bool, Reducer func(any, any) any.

Two things to know before using it

• Everything is []any. Gno has no generics, so element access means a type assertion in your own callback, and a wrong one panics at runtime instead of failing to compile. Keep slices homogeneous.
• Every call allocates a new slice. Chaining four operations over a large collection allocates four times. That is fine for rendering a page and wrong for a hot path over persisted state, where a single explicit loop is both cheaper and clearer.

GroupBy returns map[any][]any, so the key must be a comparable type.

Part of moul/gno-contracts — moul's versioned gno.land contracts. See the repository for the full catalog, build/test tooling, and usage.

⚠️ Disclaimer: provided as-is, without warranty; not security-audited. Full disclaimer: DISCLAIMER.