#==============================================================================
# Generic property-bag mechanism.
# Copyright (C) 2004 by Eric Sunshine <sunshine@sunshineco.com>
#
#    This library is free software; you can redistribute it and/or modify it
#    under the terms of the GNU Library General Public License as published by
#    the Free Software Foundation; either version 2 of the License, or (at your
#    option) any later version.
#
#    This library is distributed in the hope that it will be useful, but
#    WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
#    or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Library General Public
#    License for more details.
#
#    You should have received a copy of the GNU Library General Public License
#    along with this library; if not, write to the Free Software Foundation,
#    Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
#
#==============================================================================

# Property bag : name
#   Returns the value of property 'name' in container 'bag' if present, else
#   returns a null value.  'bag' and 'name' should be simple identifiers
#   composed of alphanumeric characters and underscore, and with an alphabetic
#   or an underscore as the first character.
rule Property
{
  local p = [ _PropertyName $(<) : $(>) ] ;
  return $($(p)) ;
}

# SetProperty bag : name [ : value ]
#   Add property 'name' to container 'bag'. If 'value' is not provided, sets
#   the property to "true".
rule SetProperty
{
  local p = [ _PropertyName $(<) : $(>) ] ;
  local v = $(3) ;
  if ! $(v) { v = "true" ; }
  $(p) = $(v) ;
}

# ClearProperty bag : name
#   Remove property 'name' from container 'bag'.
rule ClearProperty
{
  local p = [ _PropertyName $(<) : $(>) ] ;
  $(p) = "" ;
}


#------------------------------------------------------------------------------
# Private utilitiy rules.
#------------------------------------------------------------------------------
rule _PropertyName
{
  return "__property_$(<)_$(>)" ;
}