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For 2023 (and 2024 ...) - we are now fully retired from IT training.
We have made many, many friends over 25 years of teaching about Python, Tcl, Perl, PHP, Lua, Java, C and C++ - and MySQL, Linux and Solaris/SunOS too. Our training notes are now very much out of date, but due to upward compatability most of our examples remain operational and even relevant ad you are welcome to make us if them "as seen" and at your own risk.

Lisa and I (Graham) now live in what was our training centre in Melksham - happy to meet with former delegates here - but do check ahead before coming round. We are far from inactive - rather, enjoying the times that we are retired but still healthy enough in mind and body to be active!

I am also active in many other area and still look after a lot of web sites - you can find an index ((here))
Sparse and Greedy matching - Tcl 8.4

Problem Analysis Once you have done a sparse or greedy count, all your following counts will also be sparse or greedy - this is a well documented bug in Tcl 8.4!

Reminder ...
.* is a greedy match - any character and AS MANY AS POSSIBLE
.*? is a sparse match - any character but AS FEW AS POSSIBLE

set demo abc@def@ghi@jkl
#
# Correctly working greedy matches
regexp (.*)@(.*) $demo all first second
puts "$first and $second"
#
# Correctly working sparse matches
regexp (.*?)@(.*?) $demo all first second
puts "$first and $second"
#
# Both matches will be SPARSE here
regexp (.*?)@(.*) $demo all first second
puts "$first and $second"
#
# Both matches will be GREEDY here
regexp (.*)@(.*?) $demo all first second
puts "$first and $second"


Running that, we get:

earth-wind-and-fire:~/oct07/camb grahamellis$ tclsh spag
abc@def@ghi and jkl
abc and
abc and
abc@def@ghi and jkl
earth-wind-and-fire:~/oct07/camb grahamellis$


Suggested Work-around

You can emulate a sparse match by excluding the delimiter character from he group that you would be sparse matching, and using a greedy match.

Thus
regexp (.*?)@(.*) $demo all first second
can be rewritten as
regexp {([^@]*)@(.*)} $demo all first second
if you really needed sparse followed by greedy!

result:
abc and def@ghi@jkl

(written 2007-10-27, updated 2011-03-01)

 
Associated topics are indexed as below, or enter http://melksh.am/nnnn for individual articles
T247 - Tcl/Tk - Advanced Regular Expressions
  [943] Matching within multiline strings, and ignoring case in regular expressions - (2006-11-25)
  [1195] Regular Express Primer - (2007-05-20)
  [1305] Regular expressions made easy - building from components - (2007-08-16)
  [1336] Ignore case in Regular Expression - (2007-09-08)
  [1410] Tcl / regsub - changing a string and using interesting bits - (2007-10-27)
  [1613] Regular expression for 6 digits OR 25 digits - (2008-04-16)
  [4205] Regular Expression Substitution - Tcl - (2013-11-12)


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