proplogic

A lightweight JavaScript library for tokenizing, formatting, and validating propositional logic expressions.

Installation

npm install proplogic

Quick Start

import { lexp } from 'proplogic';

lexp.validate('P∧Q');   // true
lexp.validate('P∧');    // false
lexp.validate('P & Q'); // true

API

lexp.validate(expression)

Validates whether a string is a well-formed propositional logic formula.

Parameters

• expression {string} — the formula to validate.

Returns {boolean} — true if the formula is well-formed, false otherwise.

Whitespace is ignored. Invalid or unrecognized characters return false.

lexp.validate('P∧Q');     // true
lexp.validate('(P∨Q)→R'); // true
lexp.validate('¬(¬P)');   // true
lexp.validate('∧P');      // false
lexp.validate('P∧∧Q');    // false
lexp.validate(')(P)');    // false

lexp.tokenize(expression)

Tokenizes a propositional logic expression into an array of typed tokens.

Parameters

• expression {string} — the expression to tokenize.

Returns {Array<{type: string, value: string}>} — an array of token objects, or false if the expression contains invalid characters.

Throws Error - Expression can not be formatted.

Token types: operand, operator, not, open, close.

lexp.tokenize('P∧Q');
// [
//   { type: 'operand',  value: 'P' },
//   { type: 'operator', value: '∧' },
//   { type: 'operand',  value: 'Q' }
// ]

lexp.tokenize('P & Q');
// [
//   { type: 'operand',  value: 'P' },
//   { type: 'operator', value: '∧' },  ← alias normalized
//   { type: 'operand',  value: 'Q' }
// ]

lexp.format(expression)

Normalizes an expression by stripping whitespace and replacing ASCII aliases with their canonical Unicode symbols.

Parameters

• expression {string} — the expression to format.

Returns {string} — the normalized expression.

Throws Error — Expression can not te formatted.

lexp.format('P & Q');  // 'P∧Q'
lexp.format('P | Q');  // 'P∨Q'
lexp.format('!P > Q'); // '¬P→Q'
lexp.format('P = Q');  // 'P↔Q'

confusablesTable

An exported object mapping ASCII aliases and Unicode lookalikes to their canonical logic symbols. Useful for displaying supported input formats to users.

import { confusablesTable } from 'proplogic';

console.log(confusablesTable);
// { 'V': '∨', 'v': '∨', '&': '∧', '^': '∧', '~': '¬', '!': '¬', ... }

Supported Symbols

Operators

| Symbol | Meaning | ASCII Aliases | |--------|---------|---------------| | ∧ | Conjunction (AND) | &, ^, · | | ∨ | Disjunction (OR) | v, V, \|, ∥ | | → | Implication | >, ⇒, ⊃ | | ↔ | Biconditional | =, ⇔, ⟺ | | ↮ | Not Equals | ≢, ⇎ | | ⊻ | Exclusive OR (XOR) | +, ⊕ | | ⊽ | NAND | ↑ | | ⊽ | NOR | ↓ | | ¬ | Negation (NOT) | ~, ! |

Grouping

| Symbol | Meaning | Aliases | |--------|---------|---------| | ( | Open parenthesis | [, {, （, ﹙ | | ) | Close parenthesis | ], }, ）, ﹚ |

Operands

Any single character matching [A-Za-z] or falling in the Unicode Greek block (U+0370–U+03FF) is treated as an operand (e.g., P, q, α, φ).

Testing

npm run test

Tests are run with Bun. Make sure you have Bun installed before running them.

curl -fsSL https://bun.sh/install | bash

Contributing

Feel free to open a PR or create an issue at repository link.

Additions to the characters map or confusables are welcome, as well as code changes.

License

MIT