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RE: st: RE: listtex header (AND A BUG/FEATURE IN THE MACRO LANGUAGE)


From   "Newson, Roger B" <r.newson@imperial.ac.uk>
To   <statalist@hsphsun2.harvard.edu>
Subject   RE: st: RE: listtex header (AND A BUG/FEATURE IN THE MACRO LANGUAGE)
Date   Mon, 19 Feb 2007 10:07:55 -0000

Thanks to Ben for this information. I discovered the workaround with
-tokenize- just after sending my posting yesterday, and I think I will
use that in the next version of -listtex- (which I am working on now). 

Best wishes

Roger


Roger Newson
Lecturer in Medical Statistics
Respiratory Epidemiology and Public Health Group
National Heart and Lung Institute
Imperial College London
Royal Brompton campus
Room 33, Emmanuel Kaye Building
1B Manresa Road
London SW3 6LR
UNITED KINGDOM
Tel: +44 (0)20 7352 8121 ext 3381
Fax: +44 (0)20 7351 8322
Email: r.newson@imperial.ac.uk 
www.imperial.ac.uk/nhli/r.newson/

Opinions expressed are those of the author, not of the institution.

-----Original Message-----
From: owner-statalist@hsphsun2.harvard.edu
[mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Ben Jann
Sent: 19 February 2007 08:56
To: statalist@hsphsun2.harvard.edu
Subject: Re: st: RE: listtex header (AND A BUG/FEATURE IN THE MACRO
LANGUAGE)

I reported the 503 character ":word of" limit to Stata Tech Support in
Nov. 2005 and their answer was:

"It turns out that the -:word of- extended macro
function pulls 'tokens' off of the string as words,
and Stata's internal parser has a limit of 503
characters for a 'token'. StataCorp is looking into
changing the -:word of- extended macro function to
not be affected by this limit."

Also see:
http://www.stata.com/statalist/archive/2005-11/msg00643.html
http://www.stata.com/statalist/archive/2005-11/msg01031.html

I'm surprised that it is not fixed yet. However, there are easy
workarounds: It is always possible to use -tokenize- or -gettoken-
instead of -:word of-. (And since Stata 8 you can use the -:list
sizeof- extended macro function instead of -:word count-.)

Note that the -:subinstr- extended macro function has a similar limit,
502 characters this time (-:subinstr- aborts with error if the
replacement strings are longer than this). Unfortunately there seems
to be NO WORKAROUND in this case (apart from switching to Mata). And
this isn't fixed yet either...

ben

On 2/18/07, Newson, Roger B <r.newson@imperial.ac.uk> wrote:
> Thanks for Kit for demonstrating that the bug (or feature) also occurs
> under Linux. I think I have now found the cause of the problem in a
bug
> (or feature) of the extended macro function
>
> word # of string
>
> (see online help for extended_fcn). For some reason, this indeed seems
> to have a 503-character length limit for the output word, and to treat
> characters 504 onwards of a word in a string as being part of
subsequent
> words of the string. The following code demonstrates this:
>
> **** BEGINNING OF Stata CODE - CUT HERE
> local head ""
> forvalues i = 1/104 {
>  local head "`head'1234567890"
> }
> disp `"`head'"'
> local head1: word 1 of `head'
> disp `"`head1'"'
> local head2: word 2 of `head'
> disp `"`head2'"'
> local head3: word 3 of `head'
> disp `"`head3'"'
> local head4: word 4 of `head'
> disp `"`head4'"'
> local nword: word count `head'
>  disp "`nword'"
> **** END OF Stata CODE - CUT HERE
>
> This shows that Stata thinks that the local macro -head- contains 2
> words with 503 characters each and 1 word with 34 characters, instead
of
> containing 1 word with 1040 characters. This seems to suggest that
there
> is a 503-character limit on the length of a string token. I cannot
find
> any documentation of this limit in -help limits- or in -[P] macro-.
>
> I would definitely like to know whether this limit is a bug or a
> feature, and if there are any plans to fix it in the near future.
> -listtex- uses the extended macro functions
>
> word count string
>
> and
>
> word # of string
>
> to be able to produce multiple header or footer lines if the user
> specifies these in the -headlines()- or -footlines()- option. It is a
> pity that this ability currently comes at the price of limiting a
header
> or footer line length to 503 characters. I would like to be able to
fix
> this problem.
>
> Best wishes
>
> Roger
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