symm_difference — Calculate the symmetric difference of two regions.
symm_difference calculates the symmetric difference of two regions. Note that, internally, all regions of Region2 are united to a single region before the symmetric differences between the individual regions of Region1 and the united region are calculated. Two possible definitions of the symmetric difference can be seen in the example below. A third definition is to regard the exclusive or of the two regions.
Empty regions are valid for both parameters. On output, empty regions may result. The value of the system flag 'store_empty_region' determines the behavior in this case.
Input region 1.
Input region 2.
* Simulate the symmetric difference of Region1 and Region2 with * difference and union: difference(Region1, Region2, Diff1) difference(Region2, Region1, Diff2) union2(Diff1, Diff2, Difference) * Simulate the symmetric difference of Region1 and Region2 with * union, intersection, and difference: union2(Region1, Region2, Union) intersection(Region1, Region2, Intersection) difference(Union, Intersection, Difference)
symm_difference always returns the value 2 (H_MSG_TRUE). The behavior in case of empty input (no regions given) can be set via set_system('no_object_result',<Result>) and the behavior in case of an empty input region via set_system('empty_region_result',<Result>). If necessary, an exception is raised.
intersection, union1, union2, complement, difference