gominikanren
gominikarnen is an implementation of miniKanren in Go.
What is miniKanren
miniKanren is an embedded Domain Specific Language for logic programming.
If you are unfamiliar with miniKanren here is a great introduction video by Bodil Stokke:
If you like that, then the book, The Reasoned Schemer, explains logical programming in miniKanren by example.
If you want to delve even deeper, then this implementation is based on a very readable paper, µKanren: A Minimal Functional Core for Relational Programming, that explains the core algorithm of miniKanren.
Installation
First install Go
And then run on the command line
$ go get github.com/awalterschulze/gominikanren
Example
AppendO is a goal that appends the first two input arguments into the third input argument.
In this example we use AppendO to get all the combinations that can produce the list (cake & ice d t).
package main
import (
"github.com/awalterschulze/gominikanren/sexpr/ast"
"github.com/awalterschulze/gominikanren/micro"
"github.com/awalterschulze/gominikanren/mini"
)
func main() {
states := micro.RunGoal(
-1,
micro.CallFresh(func(x *ast.SExpr) micro.Goal {
return micro.CallFresh(func(y *ast.SExpr) micro.Goal {
return micro.ConjunctionO(
// (== ,q (cons ,x ,y))
micro.EqualO(
ast.Cons(x, ast.Cons(y, nil)),
ast.NewVariable("q"),
),
// (appendo ,x ,y (cake & ice d t))
mini.AppendO(
x,
y,
ast.NewList(
ast.NewSymbol("cake"),
ast.NewSymbol("&"),
ast.NewSymbol("ice"),
ast.NewSymbol("d"),
ast.NewSymbol("t"),
),
),
)
})
}),
)
sexprs := micro.Reify("q", states)
fmt.Println(ast.NewList(sexprs...).String())
}
//Output:
//(
// (() (cake & ice d t))
// ((cake) (& ice d t))
// ((cake &) (ice d t))
// ((cake & ice) (d t))
// ((cake & ice d) (t))
// ((cake & ice d t) ())
//)