funcutil

Documentation

Overview

Package funcutil is an internal package providing utility functions to enable functional programming idioms in Go.

Index

• func Compose[T any, S any, R any](f func(T) S, g func(S) R) func(T) R
• func Contains[T comparable](a []T, x T) bool
• func Curry2[T any, S any, R any](f func(T, S) R, x T) func(S) R
• func Curry3[T any, S any, R any, Q any](f func(T, S, R) Q, x T) func(S, R) Q
• func Exists[T any](a []T, f func(T) bool) bool
• func ExistsInMap[K comparable, T any](a map[K]T, f func(K, T) bool) bool
• func First[T any](x T, _ T) T
• func Iter[T any](a []T, f func(T))
• func Map[T any, S any](a []T, f func(T) S) []S
• func MapInPlace[T any](a []T, f func(T) T)
• func MapParallel[T any, S any](a []T, f func(T) S, numRoutines int) []S
• func MapValues[T comparable, S any](a map[T]S, f func(S) S) map[T]S
• func Merge[T comparable, S any](a map[T]S, b map[T]S, both func(x S, y S) S)
• func Retain[T comparable, R any](m map[T]R, keys []T)
• func Reverse[T any](a []T)
• func Second[T any](_ T, y T) T
• func Set[T comparable](a []T) map[T]struct{}
• func SetToOrderedSlice[T constraints.Ordered](set map[T]bool) []T
• func Union[T comparable](a map[T]bool, b map[T]bool) map[T]bool
• type Optional
  • func BindOption[T any, S any](x Optional[T], f func(T) Optional[S]) Optional[S]
  • func FindMap[T any, R any](a []T, f func(T) R, p func(R) bool) Optional[R]
  • func MapOption[T any, S any](x Optional[T], f func(T) S) Optional[S]
  • func MaybeOr[T any](x Optional[T], s Optional[T]) Optional[T]
  • func None[T any]() Optional[T]
  • func Some[T any](x T) Optional[T]

Functions

func Compose

func Compose[T any, S any, R any](f func(T) S, g func(S) R) func(T) R

Compose (f,g) returns a function h: x -> f(g(x))

func Contains

func Contains[T comparable](a []T, x T) bool

Contains returns true when there is some y in slice a such that x == y

func Curry2

func Curry2[T any, S any, R any](f func(T, S) R, x T) func(S) R

Curry2 is for currying functions. with two arguments

func Curry3

func Curry3[T any, S any, R any, Q any](f func(T, S, R) Q, x T) func(S, R) Q

Curry3 is for currying functions. with three arguments

func Exists

func Exists[T any](a []T, f func(T) bool) bool

Exists returns true when there exists some x in slice a such that f(x), otherwise false.

func ExistsInMap

func ExistsInMap[K comparable, T any](a map[K]T, f func(K, T) bool) bool

ExistsInMap returns true when there exists some k,x in map a such that f(k,x), otherwise false.

func First

func First[T any](x T, _ T) T

First returns the first of two arguments

func Iter

func Iter[T any](a []T, f func(T))

Iter iterates over all elements in the slice and call the function on that element.

func Map

func Map[T any, S any](a []T, f func(T) S) []S

Map returns a new slice b such for any i <= len(a), b[i] = f(a[i])

func MapInPlace

func MapInPlace[T any](a []T, f func(T) T)

MapInPlace iterates over all elements in the slice and call the function on that element to update it.

func MapParallel

func MapParallel[T any, S any](a []T, f func(T) S, numRoutines int) []S

MapParallel is a parallel version of Map using numRoutines goroutines.

func MapValues

func MapValues[T comparable, S any](a map[T]S, f func(S) S) map[T]S

MapValues returns a new slice b such for any i <= len(a), b[i] = f(a[i])

func Merge

func Merge[T comparable, S any](a map[T]S, b map[T]S, both func(x S, y S) S)

Merge merges the two maps into the first map. if x is in b but not in a, then a[x] := b[x] if x in both in a and b, then a[x] := both(a[x], b[x]) @mutates a

func Retain

func Retain[T comparable, R any](m map[T]R, keys []T)

Retain removes all the key-value pairs in m where the key is not in keys.

func Reverse

func Reverse[T any](a []T)

Reverse returns the reversed slice

func Second

func Second[T any](_ T, y T) T

Second returns the first of two arguments

func Set

func Set[T comparable](a []T) map[T]struct{}

Set takes an array of elements and returns a set of those elements, represented as a map from elements to empty struct

func SetToOrderedSlice

func SetToOrderedSlice[T constraints.Ordered](set map[T]bool) []T

SetToOrderedSlice converts a set represented as a map from elements to booleans into a slice. Sorts the result in increasing order

func Union

func Union[T comparable](a map[T]bool, b map[T]bool) map[T]bool

Union returns the union of map-represented sets a and b. This mutates map a @mutates a

Types

type Optional

type Optional[T any] interface {
	// ValueOr returns the value of the optional if it is some value, otherwise the default value if it is none
	ValueOr(defaultVal T) T

	// Value returns the value or panics if it is none
	Value() T

	// IsSome returns true if the optional represents some value
	IsSome() bool

	// IsNone returns true is the optional is none
	IsNone() bool
}

An Optional holds a value or none. If it has a value, the IsSome returns true and IsNone returns false.

func BindOption

func BindOption[T any, S any](x Optional[T], f func(T) Optional[S]) Optional[S]

BindOption is the monadic bind operation on optional values

func FindMap

func FindMap[T any, R any](a []T, f func(T) R, p func(R) bool) Optional[R]

FindMap returns Some(f(x)) when there exists some x in slice a such that p(f(x)), otherwise None.

func MapOption

func MapOption[T any, S any](x Optional[T], f func(T) S) Optional[S]

MapOption is the map monadic operation on optional values

func MaybeOr

func MaybeOr[T any](x Optional[T], s Optional[T]) Optional[T]

MaybeOr returns the first optional that is some. If both are none, then the returned value is none

func None

func None[T any]() Optional[T]

None creates an optional value with no value in it

func Some

func Some[T any](x T) Optional[T]

Some creates an optional value with some value in it.