xerocross.vulcan

This is a fork of RyanMarcus/vulcan. It will remain mostly unchanged, but that project had not been updated in 3 years and I needed to update the npm package for my own use.

Vulcan


A library for proving statements in propositional logic using resolution.

Vulcan uses a modified version of the excellent lexer and parse from llang.

For examples, see the tests or this blog post.

Simple usage example

``javascript
// We are using const for imports because the reference will never change.
// See more here: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/const

const vulcan = require("vulcan");
const proof = vulcan.prove(["A -> B", // the knowledgebase
"B -> C",
"C -> D",
"D -> E"],
"B -> D"); // the query

console.log(vulcan.isProofComplete(proof));
console.log(proof)
``

Will output:

`
true
[ { label: 'inital expression', tree: '(A -> B)', idx: 0 },
{ label: 'eliminate implication', tree: '(!A | B)', idx: 1 },
{ label: 'inital expression', tree: '(B -> C)', idx: 2 },
{ label: 'eliminate implication', tree: '(!B | C)', idx: 3 },
{ label: 'inital expression', tree: '(C -> D)', idx: 4 },
{ label: 'eliminate implication', tree: '(!C | D)', idx: 5 },
{ label: 'inital expression', tree: '(D -> E)', idx: 6 },
{ label: 'eliminate implication', tree: '(!D | E)', idx: 7 },
{ label: 'knowledge base clause from 1',
tree: '(!A | B)',
idx: 8 },
{ label: 'knowledge base clause from 3',
tree: '(!B | C)',
idx: 9 },
{ label: 'knowledge base clause from 5',
tree: '(!C | D)',
idx: 10 },
{ label: 'assume for a contradiction', tree: 'B', idx: 12 },
{ label: 'assume for a contradiction', tree: '!D', idx: 13 },
{ label: 'resolve of 9 and 12',
tree: 'C',
idx: 22,
req: [ 9, 12 ] },
{ label: 'resolve of 10 and 13',
tree: '!C',
idx: 27,
req: [ 10, 13 ] },
{ label: 'resolve of 22 and 27',
tree: false,
idx: 109,
req: [ 22, 27 ] } ]
``