What is this?

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

• Standards-compliant:

• Easy to integrate: database/sql-like Go API
• Highly customizable:

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

go get -u github.com/ichiban/prolog

Usage

Instantiate an interpreter

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

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

// See examples/sandboxing/main.go for details.
p := new(prolog.Interpreter)

Load a Prolog program

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.

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

Run the Prolog program

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:

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 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:

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

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

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

Extensions

• predicates: Native predicates for ichiban/prolog.
• kagomelog: a Japanese morphological analyzing predicate.

License

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

Contributing

See ARCHITECTURE.md for architecture details.

• Fork it (https://github.com/ichiban/prolog/fork)
• Create your feature branch (git checkout -b feature/fooBar)
• Commit your changes (git commit -am 'Add some fooBar')
• Push to the branch (git push origin feature/fooBar)
• Create a new Pull Request

Acknowledgments

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

• guregu for contributing code and ideas
• Markus Triska for his deep knowledge and insights on modern Prolog, as evidenced by his insightful comments on issues
• Prof. Ulrich Neumerkel for valuable guidance, his works on ISO standards, the Prologue for Prolog, and DCGs.