λ

λ is a functional programming framework for go, which adds support for an alternative error handling workflow using options.

Notes

This package requires at least a Go version of 1.6 to compile succesfully.

Example usage

Read all lines from stdin

package main

import (
	"fmt"
	λ "github.com/4thel00z/lambda/v1"
	"os"
)

func main() {
	content := λ.Slurp(os.Stdin).UnwrapString()
	// do things with content...
}

Read a file and pipe it to stdout

package main

import (
	λ "github.com/4thel00z/lambda/v1"
	"os"
)

func main() {
	λ.Open("lorem_ipsum.txt").Slurp().WriteString(os.Stdout)
}

Read a JSON file into a struct

package main

import (
	λ "github.com/4thel00z/lambda/v1"
	"strings"
	"fmt"
)

type MagicSpell struct {
	Name        string  `json:"name"`
	AttackPower float64 `json:"attack_power"`
	Type        string  `json:"type"`
	Description string  `json:"description"`
}

func main() {
	var (
		m MagicSpell
	)
	λ.Open("magic.json").Slurp().JSON(&m).Catch(λ.Die)

    fmt.Println(strings.Join([]string{m.Name, m.Type, fmt.Sprintf("%f", m.AttackPower), m.Description}, "\n"))

	// ToJSON() detects if the current value is a pointer or not
	fmt.Println(λ.WrapValue(m).ToJSON().UnwrapString())
	// Works even if you use the pointer operator again
	fmt.Println(λ.WrapValue(&m).ToJSON().UnwrapString())
}

Functional conditionals

You never need to check an error with an if clause again. Instead you can define the flow as functional chain, start point is always λ.If. You even can reuse the same chain, it doesn't contain data. You pass the data via Conditional.Do.

package main

import (
	λ "github.com/4thel00z/lambda/v1"
)

func main() {
	manipulateError := λ.Return(λ.Wrap(nil, λ.Error("this error will be thrown")))
	input := λ.Wrap(nil, λ.Error("something is weird"))
	output := λ.If(λ.HasError, manipulateError).Else(λ.Cry).Do(input)
	λ.If(λ.HasNoError, λ.Identity).Else(λ.Cry).Do(output)
}

Make Rest calls

package main

import (
	λ "github.com/4thel00z/lambda/v1"
	"os"
)

func main() {
	λ.Get("https://ransomware.host").Do().Slurp().WriteString(os.Stdout)
}

Simple AES-CBC encryption with PKC7 Padding

package main

import (
	"crypto/rand"
	λ "github.com/4thel00z/lambda/v1"
	"io"
	"strings"
)

var (
	loremIpsum = `Lorem ipsum dolor sit amet, consetetur sadipscing elitr,
sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat,
sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum.
Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet.
Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat,
sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren,
no sea takimata sanctus est Lorem ipsum dolor sit amet.`
	loremIpsumReader = strings.NewReader(loremIpsum)
)

func getRandomKey() []byte {
	key := make([]byte, 32)
	_, err := rand.Read(key)

	if err != nil {
		panic(err)
	}
	return key
}
func main() {
	key := getRandomKey()
	if λ.Read(loremIpsumReader).EncryptAES(key).DecryptAES(key).UnwrapString() != loremIpsum {
		panic("encryption and decryption doesn't work")
	}

	// test for random payload and key that enc & decryption works fine
	for i := 0; i < 10; i++ {
		key = getRandomKey()
		o := λ.Read(io.LimitReader(rand.Reader, 1024))
		text := o.UnwrapString()
		if o.EncryptAES(key).DecryptAES(key).UnwrapString() != text {
			panic("encryption and decryption doesn't work")
		}
	}

}

Pubkey cryptography

package main

import (
	λ "github.com/4thel00z/lambda/v1"
	"log"
)

func main() {
	rsa := λ.RSA(4096)
	println(rsa.ToPublicKeyPemString())
	println(rsa.ToPrivateKeyPemString())
	original := "Some important message which needs to stay secret lel"
	secretMsg := rsa.EncryptRSA(original).UnwrapString()
	if original == secretMsg {
		log.Fatalln("This encryption don't work boi!")
	}
	if original != rsa.DecryptRSA(secretMsg).UnwrapString() {
		log.Fatalln("This decryption don't work boi!")
	}

	// Use rsa.UnwrapPrivateKey() and rsa.UnwrapPublicKey() if you want to extract the raw key material
	// You can load it via λ.LoadRSA(pub,priv)

}

How to generate a sha256 checksum

package main

import (
	"bytes"
	λ "github.com/4thel00z/lambda/v1"
)

var (
	loremIpsum = `Lorem ipsum dolor sit amet, consetetur sadipscing elitr,
sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat,
sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum.
Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet.
Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat,
sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren,
no sea takimata sanctus est Lorem ipsum dolor sit amet.`
	loremIpsumReader = bytes.NewReader([]byte(loremIpsum))
)

func main() {
	expected := "70026299e7c4b3bf5b6256b2069ae0cbc2e0960cad1acb51208a311f3864d5bd"
	if λ.Read(loremIpsumReader).Checksum().UnwrapChecksum() != expected {
		panic("sha256 of loremIpsum is wrong!")
	}
}

How to render a markdown and print out to stdout

package main

import (
	λ "github.com/4thel00z/lambda/v1"
	"os"
)

func main() {
	λ.Markdown().Render(`# Markdown
This is so awesome

## Why is this section so nice
Really dunno

### Omg, can do all the things
* yeah
* all
* of
* them

#### Emojis work too:👩
#### Code aswell:
`+"```"+ `
import "github.com/charmbracelet/glamour"

r, _ := glamour.NewTermRenderer(
    // detect background color and pick either the default dark or light theme
    glamour.WithAutoStyle(),
    // wrap output at specific width
    glamour.WithWordWrap(40),
)

out, err := r.Render(in)
fmt.Print(out)
`+"```").WriteStringTo(os.Stdin)
}

License

This project is licensed under the GPL-3 license.