Re: [q-lang-users] Suggestions on how to debug?

[Albert G. <Dr....@t-...>]

Albert Graef wrote:
> Andrew Berg wrote:
>> It looks to me like "regex_next" is doing all the work, and if asked to predict, I would guess that it is tail recursive.
> 
> No, the current version is not. And yes, I guess you're right with your
> suspicion that regex_next is the culprit here. It shouldn't be a big
> deal to rewrite regex_next so that it's tail-recursive, though.

Ok, here is a tail-recursive implementation of regex. Just put this at
the beginning of your script and fetch_history "AA" goes through without
a hitch (takes a while, though). (I might also use this definition in
the next version of clib, but not right now as I haven't tested it
thoroughly yet and I don't want to hold back the 7.6 release any longer.)

special regex ~OPTS ~REGEX ~S EXPR, regex_next ~Xs EXPR;
special check ~P X Y;

regex OPTS:String REGEX:String S:String EXPR
				= check (regmatch OPTS REGEX S)
				  (reverse (regex_next [EXPR] EXPR)) [];

regex_next Xs EXPR		= check regnext
				  (regex_next [EXPR|Xs] EXPR) Xs;

check P:Bool X Y		= X if P;
				= Y otherwise;
check P X Y			= P otherwise;

Also note that using regex to just split a string at a given delimiter
is really overkill. There's the split function which does this much
faster (clib provides a C implementation of that function). To use this,
just s/regsplit "g"/split/ in your script and fetch_history "AA" runs
much faster.

HTH,
Albert

-- 
Dr. Albert Gr"af
Dept. of Music-Informatics, University of Mainz, Germany
Email:  Dr....@t-..., ag...@mu...
WWW:    http://www.musikinformatik.uni-mainz.de/ag