----- Original Message -----
- It may be useful to group contiguous operations of the same kind, i.e. a "run" of N equal characters would result in one call to the output script object, rather than N calls. This can be achieved by merging in the script object, but that would be less efficient than passing the entire run as an iterator pair:
struct output {
template <typename ITER_T> void insertion(ITER_T begin, ITER_T end) { do_something_with(begin,end); }
};
I've been mulling this over, and I have an idea that is starting to grow on me. What if we left insertion() and deletion() (and substitution) as-is: they continue to receive individual sequence elements, and operation scores. But we *do* modify the equality() method to take two ranges, in the manner you suggested above. It would introduce an asymmetry of equality() with respect to the other methods, but I think there are some real arguments for it: *) the order of insertions and deletions identified by these algorithms is not generally "consecutive" - that is, if the edit script involves a sequence of deletions and insertions, you cannot count on these being presented consecutively, and that will tend to undermine the benefit of accepting such ranges in the handling methods. *) the algorithms *do* identify consecutive runs of equal elements. *) the insertion() and deletion() methods receive operation-cost information, and it isn't trivial to fold that information into an iterator stream. *) the equality() method does *not* receive operation cost information, because that cost is always zero by definition. That means it is sensible (and easy) to simply present a range constructed of the iterators at the start and end of the equal run in question. This begin/end information for equal runs is readily available, and saves cost both internal to the algorithms, and (likely) externally as well. *) Runs of 'equal' dominate the script in most larger-scale applications of interest. Actual insertions, deletions, etc, are relatively small. Compressing equal runs in this way is where almost all of the bang/buck resides. *) This is more speculative, but just looking at how I ended up doing my 'diff' benchmark implementation, accepting ranges for insertion() and deletion() would actually have required me to do a bit *more* coding, to handle the logic of appending an incoming range of data onto my 'ins' and 'del' vectors, compared to simply push_back() as I did: https://github.com/erikerlandson/algorithm/blob/edit_distance/sequence/examp...