On 10/18/2010 1:23 PM, David Dawe wrote:
Boost Regex fails to compile a regular expression such as "{abc}" with the error
"Invalid content of repeat range". However, both Perl and PCRE accept the regular
expression, treating the "{" as a literal character.
The PCRE man page at http://www.pcre.org/pcre.txt clearly states:
An opening curly bracket that appears in a position where a quantifier
is not allowed, or one that does not match the syntax of a quantifier,
is taken as a literal character.
The Perl regular expression man page at http://perldoc.perl.org/perlre.html
is similar, though not quite as clear:
If a curly bracket occurs in any other context, it is treated as a regular
character. In particular, the lower bound is not optional.
Nevertheless, the behaviour of both PCRE and Perl are the same.
I am currently using Boost 1.39, but I have seen no mention of a change in
this area for more recent versions of Boost Regex.
And finally … my question …
Is there a way in Boost Regex to interpret a "{" as a literal character in
the above context in a Perl regular expression, while still allowing the
"{n,m}" bounded repeat in places where it is syntactically valid?
Use the backslash escape character, as in "\{" to match "{" as a literal character.