# `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.

```go
numbers := []any{1, 2, 3, 4, 5, 6}

isEven := func(v any) bool { return v.(int)%2 == 0 }
double := func(v any) any  { return v.(int) * 2 }
sum    := func(a, b any) any { return a.(int) + b.(int) }

evens  := fp.Filter(numbers, isEven)   // [2 4 6]
bigger := fp.Map(evens, double)        // [4 8 12]
total  := fp.Reduce(bigger, sum, 0)    // 24
```

## The set

| | |
| --- | --- |
| transform | `Map`, `FlatMap`, `Filter`, `Reduce` |
| test | `All`, `Any`, `None`, `Find` |
| reshape | `Chunk`, `Reverse`, `Flatten`, `Zip`, `Unzip`, `GroupBy` |

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.

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---

Part of **[moul/gno-contracts](https://github.com/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](https://github.com/moul/gno-contracts/blob/main/DISCLAIMER.md).

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