AsciiChem

AsciiChem is an ASCII syntax for representing chemistry: atoms, molecules, bonds, reactions, electron configurations, and embedded mathematics. It parses to a semantic model and renders to MathML, HTML, LaTeX, and SVG.

Why

AsciiMath is insufficient for chemistry:

Prefix superscripts/subscripts have no atom to bind to — AsciiMath forces a phantom {} carrier (e.g. {}^14C), which is semantically wrong: the isotope belongs to the atom, not to an empty element.
No native syntax for stoichiometric coefficients, reaction arrows, conditions, or spectator ions.
No representation for electron configuration, term symbols, or bonds.
No structural diagrams.

AsciiChem closes these gaps.

Installation

Add to your Gemfile:

gem "asciichem"

Or install directly:

$ gem install asciichem

Usage

require "asciichem"

formula = AsciiChem.parse("H_2O")
formula.to_mathml  # => "<math>...</math>"
formula.to_text    # => "H_2O"  (round trip)

Conformance

The reference implementation of the AsciiChem contract. Every claim is gated by the shared corpus (asciichem-tests) in CI — a level without the green corpus run behind it does not ship.

Level	Claim	Basis
L0 notation	yes	parse/reject contract; every `roundTrip` fixture returns its input
L1 semantics	yes	wire form validates against the v1 schemas and round-trips; the perception pass (implicit hydrogens, aromatic rings) is corpus-gated
L2 render	yes	MathML byte-goldens, canonical text, and the wire form for every construct
L3 stereo	yes	tetrahedral chirality, directional bonds, wedge/hash; parity-correct canonical SMILES including ring closures
L4 identity	partial	opt-in InChI engine with stereo layers, OPSIN adapter, identifier cross-check, citation bibitems; CAS source decision pending

TypeScript and Python claim the same levels they pass; see their READMEs and the levels document.

Design

See ARCHITECTURE.adoc and the specification at https://www.asciichem.org.

License

BSD-2-Clause. See LICENSE.

asciichem

Development