jog increment - problems

I have been exploring various options, but want to use the ilowpass idea.

The main idea revolves around addition of the count from the MPG and the count from a traverse button clock. This then requires a counter operated by a button, and an adder to sum the MPG and Traverse counters.
1) Adder: I can't find a hal integer adder - does one exist? I have written my own which fits my requirement.
2) Traverse counter
a) The first way I did this was to use a clock feeding into sim_encode (+- speed from switches + mux) feeding into decoder - counts.
b) The alternative way (still in progress) is to use siggen to create the pulse train, and some way to convert that to a count (encoder?)
The choice is based on which route is more lightweight in instruction cycles.

Question advice, please:

If I am asking questions that might have a more general interest, but are relating to a thread like this, is it better to post within thread, or create a new topic? e.g. a question of hal integer addition.

I mean a hal component that does integer addition.

I have a working setup.

The MPG goes through encoder to produce counts
Traverse/slew switch uses a clock from siggen, and a counter (with up/down control)
These two are fed into a summer (integer) to produce the total count.  
I had to write some integer hal components.

The next step is to use ilowpass.

I have a prototype box that will be fitted to the apron. The idea is to have a lathe that is as similar in operation to the original but using a stepper for z, so that I can then use linuxcnc for screw cutting.

If anybody is interested I could post more details.