fp-go - Functional Programming for Go

GitHub stars

50+

Contributors

95%

Test coverage

Dependencies

Capabilities

Functional primitives, built for the Go developer experience.

Fast & idiomatic

Generics-native. No reflection, no runtime cost. Feels like plain Go.

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Type-safe

Option, Either, Result, Try — full inference. Never interface{} again.

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Composable

Pipe, compose, fold. Build readable pipelines from one-screen functions.

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Battle-tested

Powers data pipelines at IBM and beyond. 95% coverage, fuzz-tested.

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Example

Write less. Express more.

Replace if err != nil ladders with typed flows. Compose small, total functions into pipelines that are easy to read, refactor, and test.

01Option[T] — nullable values without nil checks.
02Either[E,A] & Result[T] — typed error flows.
03Pipe & Compose — left-to-right data transforms.
04Slice & Map helpers: filter, fold, group, partition, zip.

main.go

option.go

pipe_test.go

fp-go · greet.go

package main

import (
    "fmt"
    "strings"
    F "github.com/IBM/fp-go/v2"
    O "github.com/IBM/fp-go/v2/option"
)

// Parse → validate → format. Total, typed, nil-safe.
func greet(raw string) string {
    return F.Pipe3(
        O.FromString(raw),
        O.Filter(func(s string) bool {
            return len(s) > 1
        }),
        O.Map(strings.Title),
        O.GetOrElse(F.Constant("friend")),
    )
}

func main() {
    fmt.Println("Hello, " + greet("ada"))
    // → Hello, Ada
}