fn

README

Functional Go 1.18 with Generics

Note: Go report card doesn't do 1.18 yet.

• Map/Filter/Reduce
• Each Loop
• Maps Library
• Map Functions Library
• Filter Functions Library

Documentation

Overview

Package fn implements the traditional map/filter/reduce/each functions and an array type (A) for those who prefer a more object-oriented approach. Unlike other implementations, the array (slice) is always first preventing the first-class in-line anonymous function from obfuscating the parameter list of the functional function.

Index

• func Filter[T any](slice []T, f func(in T) bool) []T
• func Map[I any, O any](slice []I, f func(in I) O) []O
• func Reduce[T any, R any](slice []T, f func(in T, ref *R)) *R
• func Reverse[T any](list []T) chan T
• type A
  • func (a A[any]) E(f func(i any))
  • func (a A[any]) Each(f func(i any))
  • func (a A[any]) F(f func(i any) bool) A[any]
  • func (a A[any]) Filter(f func(i any) bool) A[any]
  • func (a A[any]) Log()
  • func (a A[any]) Logf(f string)
  • func (a A[any]) M(f func(i any) any) A[any]
  • func (a A[any]) Map(f func(i any) any) A[any]
  • func (a A[any]) Print()
  • func (a A[any]) Printf(t string)
  • func (a A[any]) Println()
  • func (a A[any]) R(f func(i any, r *any)) *any
  • func (a A[any]) Reduce(f func(i any, r *any)) *any
• type Number
• type Sharable
• type Text

Examples

• A (A_is_for_array)
• A.Each
• A.Filter
• A.Log
• A.Map
• A.Print
• A.Reduce
• Reverse

Functions

func Filter

func Filter[T any](slice []T, f func(in T) bool) []T

Filter applies the boolean function on each item only returning those items that evaluate to true.

func Map

func Map[I any, O any](slice []I, f func(in I) O) []O

Map executes an operator function provided on each item in the slice returning a new slice with items of a potentially different type completely (which is different from using the Array.Map method which requires returning the same type). If error handling is needed it should be handled within an enclosure within the function. This keeps signatures simple and functional.

func Reduce

func Reduce[T any, R any](slice []T, f func(in T, ref *R)) *R

Reduce calls the given reducer function for every item in the slice passing a required reference to an item to hold the results If error handling is needed it should be handled within an enclosure within the function. This keeps signatures simple and functional.

func Reverse

func Reverse[T any](list []T) chan T

Reverse reverses the order of any slice passed to it.

Example

package main

import (
	"fmt"

	"github.com/rwxrob/fn"
)

func main() {
	strings := []string{"a", "b", "c", "d"}
	for e := range fn.Reverse(strings) {
		fmt.Print(e)
	}
	fmt.Println()
	ints := []int{1, 2, 3, 4}
	for e := range fn.Reverse(ints) {
		fmt.Print(e)
	}
	fmt.Println()
	anys := []any{1, "two", 3.3, '4'}
	for e := range fn.Reverse(anys) {
		fmt.Print(e)
	}
}

Output:
dcba
4321
523.3two1

Types

type A

type A[T any] []T

A is the equivalent of an array primitive in other functional languages. It is a generic slice of anything.

Example (A_is_for_array)

package main

import (
	"fmt"

	"github.com/rwxrob/fn"
)

func main() {
	fn.A[int]{1, 2, 3}.Print()
	fmt.Println()
	fn.A[string]{"one", "two", "three"}.Println()
}

Output:
123
one
two
three

func (A[any]) E

func (a A[any]) E(f func(i any))

E calls Do function on self.

func (A[any]) Each

func (a A[any]) Each(f func(i any))

Each calls each.Do on self

Example

package main

import (
	"fmt"

	"github.com/rwxrob/fn"
)

func main() {
	fn.A[int]{1, 2, 3}.Each(func(i int) { fmt.Print(i) })
	fn.A[int]{1, 2, 3}.E(func(i int) { fmt.Print(i) })
}

Output:
123123

func (A[any]) F

func (a A[any]) F(f func(i any) bool) A[any]

Filter calls Filter function on self.

func (A[any]) Filter

func (a A[any]) Filter(f func(i any) bool) A[any]

Filter calls Filter function on self.

Example

package main

import (
	"github.com/rwxrob/fn"
)

func main() {
	GtTwo := func(i int) bool { return i > 2 }
	LtFour := func(i int) bool { return i < 4 }
	fn.A[int]{1, 2, 3, 4}.Filter(GtTwo).Print()
	fn.A[int]{1, 2, 3, 4}.F(GtTwo).F(LtFour).Print()
}

Output:
343

func (A[any]) Log

func (a A[any]) Log()

Log calls each.Log on self.

Example

package main

import (
	"log"
	"os"

	"github.com/rwxrob/fn"
)

func main() {
	log.SetOutput(os.Stdout)
	log.SetFlags(0)
	fn.A[int]{1, 2}.Log()
	fn.A[int]{1, 2}.Logf("some: %v")
}

Output:
1
2
some: 1
some: 2

func (A[any]) Logf

func (a A[any]) Logf(f string)

Logf calls each.Logf on self.

func (A[any]) M

func (a A[any]) M(f func(i any) any) A[any]

M calls Map function on self.

func (A[any]) Map

func (a A[any]) Map(f func(i any) any) A[any]

Map calls Map function on self.

Example

package main

import (
	"github.com/rwxrob/fn"
)

func main() {
	AddOne := func(i int) int { return i + 1 }
	fn.A[int]{1, 2, 3}.Map(AddOne).Print()
	fn.A[int]{1, 2, 3}.M(AddOne).M(AddOne).Print()
}

Output:
234345

func (A[any]) Print

func (a A[any]) Print()

Print calls each.Print on self.

Example

package main

import (
	"github.com/rwxrob/fn"
)

func main() {
	fn.A[int]{1, 2}.Println()
	fn.A[int]{1, 2}.Printf("some: %v\n")
	fn.A[int]{1, 2}.Print()
}

Output:
1
2
some: 1
some: 2
12

func (A[any]) Printf

func (a A[any]) Printf(t string)

Printf calls each.Printf on self.

func (A[any]) Println

func (a A[any]) Println()

Println calls each.Println on self.

func (A[any]) R

func (a A[any]) R(f func(i any, r *any)) *any

Reduce calls Reduce function on self.

func (A[any]) Reduce

func (a A[any]) Reduce(f func(i any, r *any)) *any

Reduce calls Reduce function on self.

Example

package main

import (
	"fmt"

	"github.com/rwxrob/fn"
)

func main() {
	Sum := func(i int, a *int) { *a += i }
	fmt.Println(*fn.A[int]{1, 2}.Reduce(Sum))
	fmt.Println(*fn.A[int]{1, 2, 3, 4, 5}.R(Sum))
}

Output:
3
15

type Number

type Number interface {
	int | int64 | int32 | int16 | int8 |
		uint64 | uint32 | uint16 | uint8 |
		float64 | float32
}

Number combines the primitives generally considered numbers by JSON and other high-level structure data representations.

type Sharable

type Sharable interface {
	int | int64 | int32 | int16 | int8 |
		uint64 | uint32 | uint16 | uint8 |
		float64 | float32 |
		[]byte | string |
		bool
}

Sharable are the types that have representations in JSON, YAML, TOML and other high-level structured data representations.

type Text

type Text interface {
	[]byte | string | []rune
}

Text combines byte slice and string.