code: private boolean shouldExtendLadder(Ladder ladder, BetaBridge b) {
  
  		//Only extend if they are of the same type
  		boolean sameType = b.type.equals(ladder.btype);
  		if (!sameType) return false;
  
  		//Only extend if residue 1 is sequential to ladder strand
  		boolean sequential = (b.partner1 == ladder.to+1);
  		if (!sequential) return false;
  
  		switch(b.type){
  		case parallel:
  			//Residue 2 should be sequential to second strand
  			if (b.partner2 == ladder.lto+1) return true;
  			break;
  		case antiparallel:
  			//Residue 2 should be previous to second strand
  			if (b.partner2 == ladder.lfrom-1) return true;
  			break;
  		}
  		return false;
  	}
docs: Conditions to extend a ladder with a given beta Bridge:
  <li>The bridge and ladder are of the same type.
  <li>The smallest bridge residue is sequential to the first
  strand ladder.
  <li>The second bridge residue is either sequential (parallel)
  or previous (antiparallel) to the second strand of the ladder
  </li>
  @param ladder the ladder candidate to extend
  @param b the beta bridge that would extend the ladder
  @return true if the bridge b extends the ladder