fn

Type-safe functional programming primitives for Go.

Install

go get github.com/denzelpenzel/fn

Quick Start

package main

import (
    "fmt"
    "github.com/denzelpenzel/fn"
)

func main() {
    // Option — explicit presence/absence
    name := fn.Some("Alice")
    fmt.Println(name.UnwrapOr("unknown")) // Alice

    // Result — success or error
    r := fn.NewResult(42, nil)
    fmt.Println(r.IsOk()) // true

    // Slice ops — generic map, filter, fold
    doubled := fn.Map(func(x int) int { return x * 2 }, []int{1, 2, 3})
    fmt.Println(doubled) // [2 4 6]

    // Set — union, intersect, diff
    s := fn.NewSet(1, 2, 3).Union(fn.NewSet(3, 4))
    fmt.Println(s.Contains(4)) // true
}

API Overview

Category	Key Types / Functions
Core	Unit, Eq, Neq, Comp, Iden, Const
Tuple	T2, NewT2, Pair, MapFirst, MapSecond
Option	Option, Some, None, MapOption, FlatMapOption, ElimOption, LiftA2Option
Either	Either, NewLeft, NewRight, ElimEither, MapLeft, MapRight
Result	Result, Ok, Err, NewResult, MapResultOk, FlatMapResult, LiftA2Result
ResultOpt	ResultOpt, OkOpt, NoneOpt, ErrOpt
Predicate	Pred, PredAnd, PredOr, PredNot
Slice	Map, Filter, Foldl, Foldr, Find, ZipWith, Flatten, Sum, All, Any, Head, Tail, Span, SplitAt, CollectResults, TraverseResult
Set	Set, NewSet, Add, Remove, Contains, Union, Intersect, Diff, Subset
Map	KeySet, NewSubMap, NewSubMapIntersect
List	List, NewList, PushBack, PushFront, Remove, Front, Back
Queue	Queue, NewQueue, Enqueue, Dequeue, Peek
Iterator	Collect, CollectErr
Channel	SendOrQuit, RecvOrTimeout, RecvResp, Req, NewReq
Concurrency	GoroutineManager, ContextGuard, ConcurrentQueue, EventDistributor, EventReceiver
I/O	WriteFile, WriteFileRemove
Testing	GuardTest

Requirements

• Go 1.25+
• Zero dependencies

Contributing

1. Fork the repository
2. Create a feature branch
3. make test — all tests must pass
4. make lint — code must be lint-clean
5. Open a pull request

License

MIT