On Sun, 10 Jan 2010 04:55:10 +0000, joel wrote:


Ron: have you ever looked at the 1970's unix manual volume 2b under the
YACC topic. See this webpage. Look for the link for the PDF files and
use the link : v7vol2b.pdf (819KB)

Webpage
'7th Edition Manual PDF'
(http://plan9.bell-labs.com/7thEdMan/bswv7.html)

pdf file
http://plan9.bell-labs.com/7thEdMan/v7vol2b.pdf



It is the only good description of pattern matching that I have ever
seen.

The question mark indicates any single character.


I have not looked at that reference. However, if that is what it says, it is
wrong.

The question mark "?": makes the preceding item optional. Greedy, so the
optional item is included in the match if possible.

=================================
Looking at the reference you provided, I see that you have misread it. It does
*NOT* read, as you claim, that "the question mark indicates any single
character". It states the almost the SAME definition as *I* posted above:

"Optional Expressions . The operator ? indicates an optional element of an
expression. Thus ab?c matches either ac or abc."
===================================

There are some instances where "?" represents any single character, but it does
NOT do this with regard to regular expressions. Perhaps that is where you got
confused.



There are a number of problems with the above search string

1) why do you care that a blank occurs immediately after the last
digit. what happens if there is a return, tab or end of file

I don't know what you mean by a "blank". Perhaps you are confusing the use of
the "\b" token? Check that definition (which I previously posted). It is also
does NOT seem to be part of the LEX regular expression flavor which you are
quoting. Rather, in LEX, it would mean a backspace; but that is not the case
with more commonly used flavors.

2) The match is looking for a positive or negative sign folowed by any
character followed by a blank. Most people don't have a blank.

No it is not. See above. You are misinterpreting "\b".\



\d+|([-+]\d+)

It is where I found the saying

If you can't bring Mohammed to the mountain, bring the mountain to
Mohammed.

If Mohammed goes to the wrong mountain, he may get the wrong information.

You might try some of these "mountains", if the links are still valid:

Regular Expressions
http://www.regular-expressions.info/reference.html
http://support.microsoft.com/default...02&Product=vbb
http://msdn2.microsoft.com/en-us/library/6wzad2b2.aspx
http://msdn2.microsoft.com/en-us/library/ms974619.aspx
http://www.regex-guru.info/
--ron