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https://github.com/ichiban/prolog

The only reasonable scripting engine for Go.
https://github.com/ichiban/prolog

go golang interpreter logic-programming prolog

Last synced: 24 days ago
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The only reasonable scripting engine for Go.

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# ![prolog - the only reasonable scripting engine for Go](prolog.gif)



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## What is this?



`ichiban/prolog` is an embeddable **ISO Prolog** interpreter in **Go**.



- **Standards-compliant:**

  - [ISO/IEC 13211-1:1995 Information technology — Programming languages — Prolog — Part 1: General core](https://www.iso.org/standard/21413.html)

  - [A Prologue for Prolog](http://www.complang.tuwien.ac.at/ulrich/iso-prolog/prologue)

  - [DCGs](https://www.complang.tuwien.ac.at/ulrich/iso-prolog/dcgs/dcgsdraft-2019-06-03.pdf)

- **Easy to integrate:** `database/sql`-like Go API

- **Highly customizable:**

  - Sandboxing

  - Custom predicates in Go

  - Custom terms (data types) in Go



## Comparison with Other Libraries



|             | **prolog**             | otto            | go-lua          |

| ----------- | ---------------------- | --------------- | --------------- |

| Language    | ISO Prolog             | ECMA Script     | Lua             |

| Paradigm    | 🎓 Logic               | Object-oriented | Object-oriented |

| Go API      | 😻 `database/sql`-like | original        | original        |

| Declarative | ✅                     | ❌              | ❌              |

| Sandboxing  | ✅                     | ❌              | ✅              |



## Getting started



### Install latest version



```console

go get -u github.com/ichiban/prolog

```



### Usage



#### Instantiate an interpreter



```go

p := prolog.New(os.Stdin, os.Stdout) // Or `prolog.New(nil, nil)` if you don't need user_input/user_output.

```



Or, if you want a sandbox interpreter without any built-in predicates:



```go

// See examples/sandboxing/main.go for details.

p := new(prolog.Interpreter)

```



#### Load a Prolog program



```go

if err := p.Exec(`

	human(socrates).       % This is a fact.

	mortal(X) :- human(X). % This is a rule.

`); err != nil {

	panic(err)

}

```



Similar to `database/sql`, you can use placeholder `?` to insert Go data as Prolog data.



```go

if err := p.Exec(`human(?).`, "socrates"); err != nil { // Same as p.Exec(`human("socrates").`)

	panic(err)

}

```



#### Run the Prolog program



```go

sols, err := p.Query(`mortal(?).`, "socrates") // Same as p.Query(`mortal("socrates").`)

if err != nil {

	panic(err)

}

defer sols.Close()



// Iterates over solutions.

for sols.Next() {

	fmt.Printf("Yes.\n") // ==> Yes.

}



// Check if an error occurred while querying.

if err := sols.Err(); err != nil {

	panic(err)

}

```



Or, if you want to query for the variable values for each solution:



```go

sols, err := p.Query(`mortal(Who).`)

if err != nil {

	panic(err)

}

defer sols.Close()



// Iterates over solutions.

for sols.Next() {

	// Prepare a struct with fields which name corresponds with a variable in the query.

	var s struct {

		Who string

	}

	if err := sols.Scan(&s); err != nil {

		panic(err)

	}

	fmt.Printf("Who = %s\n", s.Who) // ==> Who = socrates

}



// Check if an error occurred while querying.

if err := sols.Err(); err != nil {

	panic(err)

}

```



## The Default Language



`ichiban/prolog` adheres the ISO standard and comes with the ISO predicates as well as the Prologue for Prolog and DCG predicates.



See [the Wiki](https://github.com/ichiban/prolog/wiki) for the directives and the built-in predicates.



### Top Level



`1pl` is an experimental top level command for testing the default language and its compliance to the ISO standard.



You can install it with `go install`:



```console

go install github.com/ichiban/prolog/cmd/1pl@latest

```



Then, you can enter the top level with `1pl`:



```console

$(go env GOPATH)/bin/1pl [...]

```



## Extensions



- **[predicates](https://github.com/guregu/predicates):** Native predicates for ichiban/prolog.

- **[kagomelog](https://github.com/ichiban/kagomelog):** a Japanese morphological analyzing predicate.



## License



Distributed under the MIT license. See `LICENSE` for more information.



## Contributing



See `ARCHITECTURE.md` for architecture details.



1. Fork it (https://github.com/ichiban/prolog/fork)

2. Create your feature branch (git checkout -b feature/fooBar)

3. Commit your changes (git commit -am 'Add some fooBar')

4. Push to the branch (git push origin feature/fooBar)

5. Create a new Pull Request



## Acknowledgments



We would like to extend our thanks to the following individuals for their contributions to this project:



- [guregu](https://github.com/guregu) for contributing code and ideas

- [Markus Triska](https://github.com/triska) for his deep knowledge and insights on modern Prolog, as evidenced by his insightful comments on issues

- [Prof. Ulrich Neumerkel](https://github.com/UWN) for valuable guidance, his [works on ISO standards](http://www.complang.tuwien.ac.at/ulrich/iso-prolog/), [the Prologue for Prolog](http://www.complang.tuwien.ac.at/ulrich/iso-prolog/prologue), and DCGs.



We are grateful for the support and contributions of everyone involved in this project. Arigatou gozaimasu!