# condition.icn: Object to track the state of conditional expansion
#   within a template.
#--

$ifndef __CONDITION_ICN__
$define __CONDITION_ICN__

$define  CONDITION_REVISION     "$Revision: 1.2 $"
$define  CONDITION_DATE         "$Date: 1995/11/03 19:55:39 $"

#================================================================
# Class Condition: each instance tracks the state of one
# conditional expansion operation within a template.  The
# `skipping' field is true if the conditional expansion is false,
# false if we are expanding the tokens within it.
#----------------------------------------------------------------
# condition  :=  Condition_New ( skipping )
#   [ returns a new condition object with fields:
#       .skipping  :=  skipping
#   ]
#--
# Condition_Is_Skipping ( condition )
#   [ if condition.skipping is &null -> fail
#   | else -> return &null
#   ]
#--
# Condition_Else ( condition )
#   [ if condition.skipping is &null ->
#       condition.skipping  :=  1
#   | else ->
#       condition.skipping  :=  &null
#   ]
#----------------------------------------------------------------
  record conditionTag (
    skipping )      # &null if we're expanding, true if we're skipping tokens


# - - -   C o n d i t i o n _ N e w   - - -

procedure Condition_New ( skipping )
  local condition

  condition           :=  conditionTag ( );
  condition.skipping  :=  skipping;

  return condition;
end # --- Condition_New ---


# - - -   C o n d i t i o n _ I s _ S k i p p i n g   - - -

procedure Condition_Is_Skipping ( condition )
  if  \ condition.skipping  then    # Are we skipping tokens?
    return                          # Yes, succeed
  else
    fail;                           # No, fail
end


# - - -   C o n d i t i o n _ E l s e   - - -

procedure Condition_Else ( condition )
  condition.skipping  :=  ( if ( / condition.skipping ) then 1 else &null );
end

$endif