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
  • A Prologue for Prolog
  • DCGs
• Easy to integrate: database/sql-like Go API
• Highly customizable:
  • Sandboxing
  • Custom predicates in Go
  • Custom terms (data types) in Go

go get -u github.com/ichiban/prolog

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:

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

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)
}

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)
}

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.

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>...]

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

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

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

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.

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