code: function fail(startPos, endPos, reason, args) {
    throw new GbsRuntimeError(startPos, endPos, reason, args);
  }
docs: /*
  This module provides the runtime support for the execution of a program.
  
  The runtime support includes:
  
  - A definition of a class RuntimeState, representing the global state
  of a program.
  
  - A definition of a class RuntimePrimitives, representing the available
  primitive functions.
  
  This file is a particular implementation, in which RuntimeState
  represents a Gobstones board, and RuntimePrimitives are the primitives
  functions and procedures available in Gobstones.
  
  Potential variants of the language might have a different notion of
  global state, and different available primitives.