Maybe

Example

package main

import (
    "fmt"

    "golang.org/x/exp/constraints"

    "github.com/go-asset/generics/list"
    "github.com/go-asset/generics/maybe"
)

func main() {
    result := list.FoldlIter(
        maybe.Just(0),
        readFromUser(),
        add[int],
    )

    resultStr := list.FoldlIter(
        maybe.Just(""),
        readFromUserStr(),
        add[string],
    )

    fmt.Println(result)
    fmt.Println(resultStr)
}

/*
 * Generic function, to add values (concatenation for string).
 */

func add[T constraints.Ordered](c maybe.Maybe[T], value maybe.Maybe[T]) maybe.Maybe[T] {
    if c.IsNothing() {
        return value
    }

    if value.IsNothing() {
        return c
    }

    return maybe.Just(c.Value() + value.Value())
}

/*
 * Helper functions to generate content, like if it's coming from a user.
 */

func readFromUser() chan maybe.Maybe[int] {
    ch := make(chan maybe.Maybe[int])

    myList := []maybe.Maybe[int]{
        maybe.Just(12),
        maybe.Just(2),
        maybe.Nothing[int](),
        maybe.Just(8),
    }

    go func() {
        for _, v := range myList {
            ch <- v
        }

        close(ch)
    }()

    return ch
}

func readFromUserStr() chan maybe.Maybe[string] {
    ch := make(chan maybe.Maybe[string])

    myList := []maybe.Maybe[string]{
        maybe.Just("asd"),
        maybe.Just("123"),
        maybe.Nothing[string](),
        maybe.Just(",./"),
    }

    go func() {
        for _, v := range myList {
            ch <- v
        }

        close(ch)
    }()

    return ch
}