/// <summary>
/// Registers an atom (e.g. numeric coefficient, variable name)
/// </summary>
/// <param name="kind">Atom unit token kind.</param>
/// <param name="atomNodeBuilder">Atom node builder function.</param>
public void Atom(TokenKind kind, AtomNodeBuilder <TValue> atomNodeBuilder)
{
Unit(kind, kind.BindLexeme(l => atomNodeBuilder(l)));
}