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https://github.com/google/starlark-go

Starlark in Go: the Starlark configuration language, implemented in Go
https://github.com/google/starlark-go

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Starlark in Go: the Starlark configuration language, implemented in Go

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README 

        



# Starlark in Go



[![Go Tests](https://github.com/google/starlark-go/actions/workflows/tests.yml/badge.svg)](https://github.com/google/starlark-go/actions/workflows/tests.yml)

[![Go Reference](https://pkg.go.dev/badge/go.starlark.net/starlark.svg)](https://pkg.go.dev/go.starlark.net/starlark)



This is the home of the _Starlark in Go_ project.

Starlark in Go is an interpreter for Starlark, implemented in Go.

Starlark was formerly known as Skylark.

The new import path for Go packages is `"go.starlark.net/starlark"`.



Starlark is a dialect of Python intended for use as a configuration language.

Like Python, it is an untyped dynamic language with high-level data

types, first-class functions with lexical scope, and garbage collection.

Unlike CPython, independent Starlark threads execute in parallel, so

Starlark workloads scale well on parallel machines.

Starlark is a small and simple language with a familiar and highly

readable syntax. You can use it as an expressive notation for

structured data, defining functions to eliminate repetition, or you

can use it to add scripting capabilities to an existing application.



A Starlark interpreter is typically embedded within a larger

application, and the application may define additional domain-specific

functions and data types beyond those provided by the core language.

For example, Starlark was originally developed for the

[Bazel build tool](https://bazel.build).

Bazel uses Starlark as the notation both for its BUILD files (like

Makefiles, these declare the executables, libraries, and tests in a

directory) and for [its macro

language](https://docs.bazel.build/versions/master/skylark/language.html),

through which Bazel is extended with custom logic to support new

languages and compilers.



## Documentation



* Language definition: [doc/spec.md](doc/spec.md)



* About the Go implementation: [doc/impl.md](doc/impl.md)



* API documentation: [pkg.go.dev/go.starlark.net/starlark](https://pkg.go.dev/go.starlark.net/starlark)



* Mailing list: [starlark-go](https://groups.google.com/forum/#!forum/starlark-go)



* Issue tracker: [https://github.com/google/starlark-go/issues](https://github.com/google/starlark-go/issues)



### Getting started



Build the code:



```shell

# check out the code and dependencies,

# and install interpreter in $GOPATH/bin

$ go install go.starlark.net/cmd/starlark@latest

```



Run the interpreter:



```console

$ cat coins.star

coins = {

  'dime': 10,

  'nickel': 5,

  'penny': 1,

  'quarter': 25,

}

print('By name:\t' + ', '.join(sorted(coins.keys())))

print('By value:\t' + ', '.join(sorted(coins.keys(), key=coins.get)))



$ starlark coins.star

By name:	dime, nickel, penny, quarter

By value:	penny, nickel, dime, quarter

```



Interact with the read-eval-print loop (REPL):



```pycon

$ starlark

>>> def fibonacci(n):

...    res = list(range(n))

...    for i in res[2:]:

...        res[i] = res[i-2] + res[i-1]

...    return res

...

>>> fibonacci(10)

[0, 1, 1, 2, 3, 5, 8, 13, 21, 34]

>>>

```



When you have finished, type `Ctrl-D` to close the REPL's input stream.



Embed the interpreter in your Go program:



```go

import "go.starlark.net/starlark"



// Execute Starlark program in a file.

thread := &starlark.Thread{Name: "my thread"}

globals, err := starlark.ExecFile(thread, "fibonacci.star", nil, nil)

if err != nil { ... }



// Retrieve a module global.

fibonacci := globals["fibonacci"]



// Call Starlark function from Go.

v, err := starlark.Call(thread, fibonacci, starlark.Tuple{starlark.MakeInt(10)}, nil)

if err != nil { ... }

fmt.Printf("fibonacci(10) = %v\n", v) // fibonacci(10) = [0, 1, 1, 2, 3, 5, 8, 13, 21, 34]

```



See [starlark/example_test.go](starlark/example_test.go) for more examples.



### Contributing



We welcome submissions but please let us know what you're working on

if you want to change or add to the Starlark repository.



Before undertaking to write something new for the Starlark project,

please file an issue or claim an existing issue.

All significant changes to the language or to the interpreter's Go

API must be discussed before they can be accepted.

This gives all participants a chance to validate the design and to

avoid duplication of effort.



Despite some differences, the Go implementation of Starlark strives to

match the behavior of [the Java implementation](https://github.com/bazelbuild/bazel)

used by Bazel and maintained by the Bazel team.

For that reason, proposals to change the language itself should

generally be directed to [the Starlark site](

https://github.com/bazelbuild/starlark/), not to the maintainers of this

project.

Only once there is consensus that a language change is desirable may

its Go implementation proceed.



We use GitHub pull requests for contributions.



Please complete Google's contributor license agreement (CLA) before

sending your first change to the project.  If you are the copyright

holder, you will need to agree to the

[individual contributor license agreement](https://cla.developers.google.com/about/google-individual),

which can be completed online.

If your organization is the copyright holder, the organization will

need to agree to the [corporate contributor license agreement](https://cla.developers.google.com/about/google-corporate).

If the copyright holder for your contribution has already completed

the agreement in connection with another Google open source project,

it does not need to be completed again.



### Stability



We reserve the right to make breaking language and API changes at this

stage in the project, although we will endeavor to keep them to a minimum.

Once the Bazel team has finalized the version 1 language specification,

we will be more rigorous with interface stability.



We aim to support the most recent four (go1.x) releases of the Go

toolchain. For example, if the latest release is go1.20, we support it

along with go1.19, go1.18, and go1.17, but not go1.16.



### Credits



Starlark was designed and implemented in Java by

Jon Brandvein,

Alan Donovan,

Laurent Le Brun,

Dmitry Lomov,

Vladimir Moskva,

François-René Rideau,

Gergely Svigruha, and

Florian Weikert,

standing on the shoulders of the Python community.

The Go implementation was written by Alan Donovan and Jay Conrod;

its scanner was derived from one written by Russ Cox.



### Legal



Starlark in Go is Copyright (c) 2018 The Bazel Authors.

All rights reserved.



It is provided under a 3-clause BSD license:

[LICENSE](https://github.com/google/starlark-go/blob/master/LICENSE).



Starlark in Go is not an official Google product.