1.15 class bool

Class bool defines represents PCE's two boolean constants: @on and @off. These objects are protected (see object->protect). No other boolean constants can be created.

See also

class constant

To be done

Methods for logical expressions are still lacking.

1.15.1 Send methods

bool ->initialise:

Generates the error !cannot_create_instances.

bool ->unlink:

The two instances of class bool cannot be unlinked as they are object->protect’ed.

1.15.2 Get methods

bool <-convert: any -> bool

The following values are converted to booleans:

0	@off
any other integer	@on
’@on’	@on
’@off’	@off
true, yes, constant<-name	@on
false, no, constant<-name	@off

bool <-negate: -> bool

Maps @on to @off and visa versa. The recogniser object below will toggle the graphical->inverted:

?- new(@toggle_inverted,
       click_gesture(left, '', single,
                     message(@receiver, inverted,
                             @receiver?inverted?negate))).