[Emc-developers] Re: Using hot comments in EMC

[Fred P. <fre...@ni...>]

dan falck wrote:

> Fred,
>
> I happened to read in the developer archives a message that you had 
> written regarding "hot comments" that could be used inside G-code in 
> EMC.  Could you elaborate further on this with some more examples?  

Hot comments are a quick and dirty way to get the interpreter to handle 
custom extensions. It lets you pass information as comments, which are 
ignored by the interpreter except that it calls the COMMENT() function 
when it encounters them. The COMMENT function is defined in 
emc/src/emctask/emccanon.cc, and if you look inside you'll see some 
stuff I put in a few years ago to log probed point values.

The interpreter reads ahead and will likely call this function before 
you really want it called. There is no easy way around this. The way 
around it is to have COMMENT put something on the interp_list, e.g., 
interp_list.append(your_new_msg) as seen throughout the rest of 
emccanon.cc. Then, in emctaskmain.cc, handle your_new_message as the 
other NML messages are handled by checkPreconditions(), 
checkPostconditions(), and issueCommand().

--Fred

-- 
Mr. Frederick M. Proctor
Group Leader, Control Systems Group
National Institute of Standards and Technology
100 Bureau Drive, Stop 8230
Gaithersburg, MD 20899-8230
301-975-3425 (voice)
301-990-9688 (fax)
fre...@ni... (email)