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))).