logic.js

JavaScript implementation of modified version of miniKanren.

Check this presentation.

Install

node.js

npm install logic_js --save

browser

<script src="logic.js"></script>

where logic.js is located at ./lib folder.

Usages

Core

const {lvar, run, and, or, eq} = require('logic_js') // or `logic` in browser

const x = lvar('x') // define logic variable with id 'x'

run(1, [x], eq(x, 1)) // query 'x' => [{x: 1}]
run(1, [x], (y=lvar())=> and(
  eq(y, 1),
  eq(x, y)
)) // => [{x: 1}]

run([x], or(eq(x, 1), eq(x, 2)))    // [{x: 1}, {x: 2}]
run([x], or(1, eq(x, 1), eq(x, 2))) // [{x: 1}]

Facts

const {facts} = require('logic_js')
// FACT
const parent = facts(['Steve', 'Bob'],      // Steve is Bob's parent
                   ['Steve', 'Henry'],    // Steve is Henry's parent
                   ['Henry', 'Alice'])    // Henry is Alice's parent
const x = lvar()
run(1, [x], parent(x, 'Alice'))      // who is Alice's parent => ['Henry']
run(2, [x], parent('Steve', x))      // who are Steve's children => ['Bob', 'Henry']

// RULE
const grandparent = (x, y)=> {
  let z = lvar()
  return and(parent(x, z), parent(z, y)) // x is z's parent and z is y's parent => x is y's parent
}

run(1, [x], grandparent(x, 'Alice'))  // who is Alice's grandparent => ['Steve']

Array manipulation

const {conso, firsto, resto,
      emptyo, membero, appendo} = require('logic_js')

const x = lvar('x'),
      y = lvar('y')

run([x], membero(x, [1, 2, 3]))
// [{x: 1}, {x: 2}, {x: 3}]

run([x, y], conso(x, y, [1, 2, 3]))
// [{x: 1, y: [2, 3]}]

run([x, y], appendo(x, y, [1, 2]))
/*
[ {x: [], y: [1, 2]},
  {x: [1], y: [2]}
  {x: [1, 2], y: []} ]
*/

Arithmetic & Comparison

const { add, sub, mul, div,
        lt, le, gt, ge } = require('logic_js')

run([x], add(2, x, 5))
// [{x: 3}]

Extra

const {succeed, fail, anyo} = require('logic_js')

run([x], and(eq(x, 1), succeed()))
// [{x: 1}]

run([x], and(eq(x, 1), fail()))
// []

run([x], or(
  eq(x, 1),
  eq(x, 2),
  eq(x, 3)
)) // [{x: 1}, {x: 2}, {x: 3}]

run([x], or(
  eq(x, 1),
  and(eq(x, 2), fail()),
  eq(x, 3)
)) // [{x: 1}, {x: 3}]

run(4, [x], anyo(or(eq(x, 1), eq(x, 2), eq(x, 3))))
// [{x: 1}, {x: 2}, {x: 3}, {x: 1}]

References

microKanren
microLogic
cKanren
aKanren
JavaScript stream
core.logic