Re: PCRE library requirement

[John W. Eaton]

On 31-Jan-2011, Rik wrote:

| The regular expression '\b\w+\b' can be simplified to just '\w+'.  However,
| I'd still like Richard to run a test if possible.  It would seem from this
| chart (http://www.regular-expressions.info/refflavors.html) that even '\w+'
| is not supported by POSIX regular expressions.  It appears that the reason
| this code works on most UNIX boxes without PCRE is that those machines have
| GNU libraries.  Thus, not having PCRE is not the equivalent of POSIX, but
| rather equals GNU regular expressions support.  So, I would have Richard
| try the following in an Octave built without PCRE.
| 
| str = "a ab abc"
| results = regexp (str, '\w+', "match")
| 
| If that fails because the actual libraries are truly POSIX compliant then I
| think we should make PCRE a requirement.  It is widely available and a
| number of patterns in the code use the very convenient '\s' or '\w'
| patterns rather than character classes.

This sort of problem seems like it will probably never end because
people will likely not check to see that their regexps perform as
expected in the absence of PCRE.  So I'm in favor of making PCRE a
requirement for building Octave, but I think we should not do that
until after 3.4 is released.

jwe