[Boost-users] [xpression] fuzzy on smatch fields

From: Lynn Allan (l_d_allan_at_[hidden])
Date: 2006-04-11 23:09:13

<alert comment="xpression newbie">

Xpressive looks very promising to be able to do some things I'm trying 
to implement. Thanks for providing and supporting it.

I was trying to figure out the fields that make up xpression 
smatch'es, and expanded the Example-1 to be more verbose. Basically, I 
tried to "unpack" as much info as I could find in the variable "what" 
to clarify some fuzziness on my part. There were some questions:

* The suffix and prefix info seemed blank. Are there accessors to get 
more info to conform to my (possibly flawed) understanding of the 
docs?

* The return from regex_id seemed to be an address (like 00323F58). Is 
that intended? Is there some accessor to get something more 
meaningful? (but I'm not clear what would be meaningful). What is the 
purpose of "regex_id" to the user of xpressive?

* With vc7.1, there were warnings unless I cast the lengths and 
positions ... is this intended?

void example1_verbose()
{
std::string hello( "hello world!" );
sregex rex = sregex::compile( "(\\w+) (\\w+)!" );
smatch what;
if( regex_match( hello, what, rex ) )
{
std::cout << "Overall Size: " << static_cast<int>(what.size()) << 
'\n';
std::cout << "Regex Id: " << what.regex_id() << '\n';
std::cout << "what[0]: " << what[0] << '\n';
std::cout << "Length(0): " << static_cast<int>(what.length(0)) << 
'\n';
std::cout << "Position(0): " << static_cast<int>(what.position(0)) << 
'\n';
std::cout << "Str(0): " << what.str(0) << '\n';
std::cout << "what[1]: " << what[1] << '\n';
std::cout << "Length(1): " << static_cast<int>(what.length(1)) << 
'\n';
std::cout << "Position(1): " << static_cast<int>(what.position(1)) << 
'\n';
std::cout << "Str(1): " << what.str(1) << '\n';
std::cout << "what[2]: " << what[2] << '\n';
std::cout << "Length(2): " << static_cast<int>(what.length(2)) << 
'\n';
std::cout << "Position(2): " << static_cast<int>(what.position(2)) << 
'\n';
std::cout << "Str(2): " << what.str(2) << '\n';
std::cout << "Prefix(): " << what.prefix() << '\n';
std::cout << "Prefix().matched: " << what.prefix().matched << '\n';
std::cout << "Prefix().length(): " << 
static_cast<int>(what.prefix().length()) << '\n';
std::cout << "Prefix().str(): " << what.prefix().str() << '\n';
std::cout << "Suffix(): " << what.suffix() << '\n';
std::cout << "Suffix().matched: " << what.suffix().matched << '\n';
std::cout << "Suffix().length(): " << 
static_cast<int>(what.suffix().length()) << '\n';
std::cout << "Suffix().str(): " << what.suffix().str() << '\n';
}
}

Example 1: Verbose:

Overall Size: 3
Regex Id: 00323F58
what[0]: hello world!
Length(0): 12
Position(0): 0
Str(0): hello world!
what[1]: hello
Length(1): 5
Position(1): 0
Str(1): hello
what[2]: world
Length(2): 5
Position(2): 6
Str(2): world
Prefix():
Prefix().matched: 0
Prefix().length(): 0
Prefix().str():
Suffix():
Suffix().matched: 0
Suffix().length(): 0
Suffix().str():

</alert>