anchor.diff:  
   === Statements
   
  -    count = database.statementCount;
  -    statement = database.statement(42);
  +[source]
  +count = database.statementCount;
  +statement = database.statement(42);
   
   A database has a `statementCount` property and a `statement` reader method.
   Currently all database access is mediated by statement indices.
  
positive.code: == Stable(r) API
  
  === General
  
  
negative.code: Statements are immutable.
  To change a database, splice in new statements; do not attempt to modify existing ones.
  
  [source]
  import { MMOMStatement } from 'smm/MMOM';
  statement.type === MMOMStatement.OPEN;
  statement.type === MMOMStatement.CLOSE;
  statement.type === MMOMStatement.CONSTANT;
  statement.type === MMOMStatement.VARIABLE;
  statement.type === MMOMStatement.DISJOINT;
  statement.type === MMOMStatement.ESSENTIAL;
  statement.type === MMOMStatement.FLOATING;
  statement.type === MMOMStatement.AXIOM;
  statement.type === MMOMStatement.PROVABLE;
  
  Statements have a type property, which is equal to the constants above for real statements.
  Fake statements also have types, but their number and roles are not currently considered stable.
  
  [source]
  string = statement.label;
  arrayString = statement.math;
  arrayString = statement.proof;
  
  Accessors for the fundamental parts of a statement.
  `math` and `proof` may be `null` on statement types for which they are not applicable;
  when they are applicable, they will always be present even if empty.
  
  [source]
  index = statement.index;
  database = statement.database;
  statement === database.statement(index);
  
  A statement which is in a database knows its database and index.
  
  