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https://github.com/choonkeat/sumtype-go
Fastest and simplest pattern matching sum types in Go. Don't be jealous of Rust anymore.
https://github.com/choonkeat/sumtype-go
algebraic-data-types codegenerator golang result-type sumtypes tagged-unions union-types
Last synced: 16 days ago
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Fastest and simplest pattern matching sum types in Go. Don't be jealous of Rust anymore.
- Host: GitHub
- URL: https://github.com/choonkeat/sumtype-go
- Owner: choonkeat
- License: mit
- Created: 2023-11-28T11:55:32.000Z (about 1 year ago)
- Default Branch: main
- Last Pushed: 2024-09-26T09:00:49.000Z (3 months ago)
- Last Synced: 2024-12-16T16:15:01.023Z (17 days ago)
- Topics: algebraic-data-types, codegenerator, golang, result-type, sumtypes, tagged-unions, union-types
- Language: Go
- Homepage:
- Size: 37.1 KB
- Stars: 2
- Watchers: 2
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE
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README
# sumtype-go
## Introduction
`sumtype-go` is a CLI tool designed to facilitate the creation and management of sum types (aka union types) in Go. This tool simplifies the process of generating boilerplate code for discriminated union types, making it easier to work with its variants in Go.
## Quick Tour
To define this sum type:
```elm
type User
= Anonymous
| Member String Time
| Admin String
```
write this Go type definition, e.g. in `declaration.go`
```go
type UserVariants struct { // be sure to suffix the name with `Variants`
Anonymous func()
Member func(email string, since time.Time)
Admin func(email string)
}
```
Execute this command to generate `User` type from your `UserVariants` struct
```sh
go install github.com/choonkeat/[email protected] # to install
sumtype-go -input declaration.go
```
To generate `declaration.boilerplate.go` and start using `User`!
```go
users := []User{
Anonymous(), // this returns a `User` value
Member("Alice", time.Now()), // this also returns a `User` value
Admin("Bob"), // this also returns a `User` value
}
```
and we can pattern match `User` values and return a different value depending on pattern matched variant
```go
userString := UserMap(user, UserVariantsMap[string]{
Anonymous: func() string {
return "Anonymous coward"
},
Member: func(email string, since time.Time) string {
return email + " (member since " + since.String() + ")"
},
Admin: func(email string) string {
return email + " (admin)"
},
})
```
or _do_ different things depending on pattern matched variant
```go
func SendReply(u User, comment Comment) {
u.Match(UserVariants{
Anonymous: func() {
// noop
},
Member: func(email string, since time.Time) {
sendEmail(email, comment)
},
Admin: func(email string) {
sendEmail(email, comment)
},
})
}
```
Refer to `example/gosumtype_1_*.go`
## Generics
We support generics too. e.g. the classic `Result` type
```elm
type Result x a
= Err x
| Ok a
```
can be defined as
```go
type ResultVariants[x, a any] struct {
Err func(err x)
Ok func(data a)
}
```
Same thing, after executing `sumtype-go` to generate the `.boilerplate.go` file, you can use
the generated `Result` like this
```go
results := []Result[string, int]{
Err[string, int]("Oops err"), // this returns a `Result` value
Ok[string, int](42), // this also returns a `Result` value
}
for i, result := range results {
HandleResult(i, result) // implement your own `func HandleResult(int, Result[string, int])`
}
```
Refer to `example/result_1_*.go`
## Installation
To install `sumtype-go`, ensure you have Go installed on your system, and then run the following command:
```sh
go install github.com/choonkeat/[email protected]
```
## Usage
After installation, you can start using `sumtype-go` by invoking it from the command line.
```
$ sumtype-go -h
Usage of sumtype-go:
-input string
Input file name
-pattern-match string
Name of the pattern match method (default "Match")
-suffix string
Suffix of the struct defining variants (default "Variants")
```
Here's a basic example of how to use it:
```
sumtype-go -input example/gosumtype_1_declaration.go
```