gust

A Rust-inspired declarative-programming and generic-type module for Golang that helps avoid bugs and improve development efficiency.

After using this package, your code style will be like this:

package examples_test

import (
	"errors"
	"fmt"

	"github.com/andeya/gust"
	"github.com/andeya/gust/iter"
	"github.com/andeya/gust/ret"
)

type Version int8

const (
	Version1 Version = iota + 1
	Version2
)

func ParseVersion(header iter.Iterator[byte]) gust.Result[Version] {
	return ret.AndThen(
		header.Next().
			OkOr("invalid header length"),
		func(b byte) gust.Result[Version] {
			switch b {
			case 1:
				return gust.Ok(Version1)
			case 2:
				return gust.Ok(Version2)
			}
			return gust.Err[Version]("invalid version")
		},
	)
}

func ExampleVersion() {
	ParseVersion(iter.FromElements[byte](1, 2, 3, 4)).
		Inspect(func(v Version) {
			fmt.Printf("working with version: %v\n", v)
		}).
		InspectErr(func(err error) {
			fmt.Printf("error parsing header: %v\n", err)
		})
	// Output:
	// working with version: 1
}

Go Version

go≥1.19

Features

gust.Result is a type that represents either a success or an error.
gust.Option is a type that represents either a value or nothing.
gust.Mutex is a better generic-type wrapper for sync.Mutex that holds a value.
gust.RWMutex is a better generic-type wrapper for sync.RWMutex that holds a value.
gust.SyncMap is a better generic-type wrapper for sync.Map.
gust.AtomicValue is a better generic-type wrapper for atomic.Value.
iter is a package that provides a generic-type iterator.
vec is a package of generic-type functions for slices.
valconv is a package that provides a generic-type value converter.
digit is a package of generic-type functions for digit.
and more...

Result

Improve func() (T,error), handle result with chain methods.

Result Example

func TestResult(t *testing.T) {
	var goodResult1 = gust.Ok(10)
	var badResult1 = gust.Err[int](10)

	// The `IsOk` and `IsErr` methods do what they say.
	assert.True(t, goodResult1.IsOk() && !goodResult1.IsErr())
	assert.True(t, badResult1.IsErr() && !badResult1.IsOk())

	// `map` consumes the `Result` and produces another.
	var goodResult2 = goodResult1.Map(func(i int) int { return i + 1 })
	var badResult2 = badResult1.Map(func(i int) int { return i - 1 })

	// Use `AndThen` to continue the computation.
	var goodResult3 = ret.AndThen(goodResult2, func(i int) gust.Result[bool] { return gust.Ok(i == 11) })

	// Use `OrElse` to handle the error.
	var _ = badResult2.OrElse(func(err error) gust.Result[int] {
		fmt.Println(err)
		return gust.Ok(20)
	})

	// Consume the result and return the contents with `Unwrap`.
	var _ = goodResult3.Unwrap()
}

Option

Improve func()(T, bool) and if *U != nil, handle value with Option type.

Type [Option] represents an optional value, and has a number of uses:

Initial values
Return values for functions that are not defined over their entire input range (partial functions)
Return value for otherwise reporting simple errors, where [None] is returned on error
Optional struct fields
Optional function arguments
Nil-able pointers

Option Example

func TestOption(t *testing.T) {
	var divide = func(numerator, denominator float64) gust.Option[float64] {
		if denominator == 0.0 {
			return gust.None[float64]()
		}
		return gust.Some(numerator / denominator)
	}
	// The return value of the function is an option
	divide(2.0, 3.0).
		Inspect(func(x float64) {
			// Pattern match to retrieve the value
			t.Log("Result:", x)
		}).
		InspectNone(func() {
			t.Log("Cannot divide by 0")
		})
}

Errable

Improve func() error, handle error with chain methods.

Errable Example

func ExampleErrable() {
	var hasErr = true
	var f = func() gust.Errable[int] {
		if hasErr {
			return gust.ToErrable(1)
		}
		return gust.NonErrable[int]()
	}
	var r = f()
	fmt.Println(r.IsErr())
	fmt.Println(r.UnwrapErr())
	fmt.Printf("%#v", r.ToError())
	// Output:
	// true
	// 1
	// &gust.errorWithVal{val:1}
}

Iterator

Feature-rich iterators.

Iterator Example

func TestAny(t *testing.T) {
	var iter = FromVec([]int{1, 2, 3})
	if !iter.Any(func(x int) bool {
		return x > 1
	}) {
		t.Error("Any failed")
	}
}