CWTGF: predicates

Predicates of writtenPAM

Finally there are the predicates. line? returns if its argument is a line (a drawline or a character or a textline) and . otherwise.


equal? is the general equality test for text-graphic objects. In order to be equal, two objects must appear the same visually irrespective of their location, orientation or size in relation to each other. And, if the two objects are characters, textlines, or patterns, then they must also have parallel tree structures.


And identical? is the location, orientation and size dependent equality test. Identical objects not only appear the same and are built the same, they are also located, oriented and sized to each other exactly; two identical objects displayed simultaneously will be precisely on top of each other (all their lines will be coincident).