MTSelection

Class MTSelection holds a reference to a single chain (3.4) and a list of a subset of its residues (3.6) that are selected.

Methods:

* access
-(NSString*)description	returns textual representation
-(unsigned long)count	count the number of residues in this selection
-(NSEnumerator*)selectedResidues	returns enumerator (9.6) over selected residues
* operations
-(id)addResidue: (MTResidue*)r	include residue (3.6) in selection
-(id)removeResidue: (MTResidue*)r	exclude residue (3.6) from selection
-(id)union:(MTSelection*)sel2	add all selected residues from sel2 to this one
-(id)difference:(MTSelection*)sel2	exclude all selected residues in sel2 from this one
* structural alignment of two selections
-(MTMatrix53*)alignTo: (MTSelection*)sel2	structurally align this selection to the other one and return the resulting transformation (4.4)
* creation
+(MTSelection*)selectionWithChain: (MTChain*)c	creates a new selection acting on chain (3.4) c