Go FlatZinc

GoFZN is a parser for FlatZinc models written in Go. The goal of this project is to foster the development of new constraint solvers in Go by providing researchers and constraint programming practitioners with a convenient way to interface their solvers with MiniZinc.

Under the hood, GoFZN is a handwritten recursive descent parser with a structure that closely mirrors the FlatZinc grammar. Its tokenizer (or lexer) is inspired by Rob Pike's talk Lexical Scanning in Go.

What's FlatZinc?

FlatZinc is a subset of MiniZinc, a high-level constraint modeling language designed to easily express and solve discrete optimization problems. Think of MiniZinc as the language humans use to write models, while FlatZinc serves as the language constraint solvers use to read and process these models.

Usage

Reading a FlatZinc Model

The easiest way to use GoFZN is to use the fzm.ParseModel function to read a fzn.Model struct from a reader (e.g. a file descriptor).

package main 

import (
    "fmt"
    "log"
    "os"
    
    "github.com/rhartert/gofzn/fzn"
)

func main() {
    file, err := os.Open("model.fzn")
    if err != nil {
        log.Fatal(err)
    }
    defer file.Close()

    model, err := fzn.ParseModel(file)
    if err != nil {
        log.Fatal(err)
    }

    fmt.Printf("Parsed model: %+v\n", model)
}

Note that GoFZN only takes care of verifying that components in the fzn.Model are syntactically correct. For example, the following variable declaration will be parsed succesfully despite having an inconsistent domain.

var 10..0: X; // domain is inconsistent

Interfacing Directly with a Solver

You can interface your solver directly with GoFZN by providing the fzn.Parse function with your own implementation of the fzn.Handler interface. The main advantage of this solution is that it completely removes the steps to build the fzn.Model struct, thus enabling a slightly more efficient use of the library.

Contributions

Contributions are welcome! Please feel free to submit a pull request or open an issue. Also, don't hesitate to reach out at [email protected] if you plan to use this parser for your own project.