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2.5.1.1 Region Predicates in CLIM

The following generic functions comprise the region predicate protocol. All classes that are subclasses of region must either inherit or implement methods for these generic functions.

The methods for region-equal , region-contains-region-p , and region-intersects-region-p will typically specialize both the region1 and region2 arguments.

region-equal [Generic Function]

Arguments: region1 region2

Summary: Returns t if the two regions region1 and region2 contain exactly the same set of points; otherwise, it returns nil .

region-contains-region-p [Generic Function]

Arguments: region1 region2

Summary: Returns t if all points in the region region2 are members of the region region1 ; otherwise, it returns nil .

region-contains-position-p [Generic Function]

Arguments: region x y

Summary: Returns t if the point at ( x, y ) is contained in the region region ; otherwise, it returns nil . Since regions in CLIM are closed, this must return t if the point at (x, y) is on the region's boundary.

region-contains-position-p is a special case of region-contains-region-p in which the region is the point ( x, y ).

region-intersects-region-p [Generic Function]

Arguments: region1 region2

Summary: Returns nil if region-intersection of the two regions region1 and region2 would be +nowhere+ ; otherwise, it returns t .


CommonLisp Interface Manager 2.0 User's Guide - 30 Jul 2004

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