code: public Value lookup(ILexNameToken name)
  	{
  		Value v = check(name);
  
  		if (v == null)
  		{
  			VdmRuntimeError.abort(name.getLocation(), 4034, "Name '" + name
  					+ "' not in scope", this);
  		}
  
  		return v;
  	}
docs: Return the value of a name, else fail. If the name is not present, a {@link ContextException} is thrown.
  
  @param name
  The name to look for.
  @return The value of the name.