Boost C++ Libraries: Ticket #1132: zero_tokens doesn't work

crazykriz@… — Wed, 24 Oct 2007 15:32:10 GMT

Can (still) verify this bug who seems to be rather old, because even in Boost 1.31.x I couldn't use the zero_tokens() option. I wrote an email to Vladimir Prus but never got an answer.

I hope this mess will be fixed in near future.

Vladimir Prus — Wed, 24 Oct 2007 15:48:30 GMT

For the record, using words like "mess" is not likely to get any fix sooner :-P

crazykriz@… — Thu, 25 Oct 2007 15:04:02 GMT

Replying to vladimir_prus:

For the record, using words like "mess" is not likely to get any fix sooner :-P

Don't mind, "mess" wasn't related to your work (which is excellent), but related to the situation ;-) But, do you know what's going wrong with zero_tokens() and multitokens()?

type changed

Vladimir Prus — Tue, 25 Mar 2008 16:19:01 GMT

type Support Requests → Bugs

summary, milestone changed

Vladimir Prus — Sat, 17 May 2008 07:28:33 GMT

summary program_options documentation error. → zero_tokens clarification
milestone To Be Determined → Boost 1.36.0

grywacz@… — Sat, 17 Jan 2009 21:11:03 GMT

The bug (at least for zero_tokens) is still there - verified with 1.34 and 1.37.

summary changed

grywacz@… — Sat, 17 Jan 2009 21:18:20 GMT

summary zero_tokens clarification → zero_tokens doesn't work

The simplest program to test with:

#include <boost/program_options.hpp> #include <iostream> #include <string> using namespace std; namespace po = boost::program_options; int main(int argc, char *argv[]) {

po::options_description desc("test"); desc.add_options()

("server", po::value<std::string>()->zero_tokens());

po::variables_map vm;

po::store(po::command_line_parser(argc, argv).options(desc).run(), vm);

}

anonymous — Thu, 08 Oct 2009 12:41:05 GMT

The problem with multitoken is still there in Boost 1.40 :-(

./a.out --email blah@blah me@somewhere
exception: in option 'email': multiple values not allowed

I could use value<vector<string> >(), but this implies that the option can occur more than one time on command line which I don't want allow in my case.

zero_token() also broken, I always get:

exception: in option 'verbose': at least one value required

s.ochsenknecht@… — Wed, 04 Nov 2009 12:41:30 GMT

I looked a bit deeper to the zero_token() issue. I found out that there is implicit_value(...) function which can be used for this feature. If an option occurs without any further tokens and this option is allowed to stay without any arguments, then this implicit value is assign:

    options_description desc;
    desc.add_options()
        ("verbose", value< int >()->implicit_value(1), "verbosity level")
        ;

Anyhow documentation has to be updated and maybe the zero_tokens() function needs to be removed. The multitoken() issue is still open.

Please comment. Thanks.

Vladimir Prus — Thu, 05 Nov 2009 09:23:25 GMT

Another way how zero_tokens is used to good effect is the 'bool_switch' function:

BOOST_PROGRAM_OPTIONS_DECL typed_value<bool>* bool_switch(bool* v) {

typed_value<bool>* r = new typed_value<bool>(v); r->default_value(0); r->zero_tokens();

return r;

}

This, together with validator for the bool types, allows to make --whatever be interpreted as 'true' value for 'whatever' option. Note this code:

BOOST_PROGRAM_OPTIONS_DECL void validate(any& v, const vector<string>& xs,

bool*, int)

{

check_first_occurrence(v); string s(get_single_string(xs, true));

The 'true' passed to 'get_single_string' means that if there are no tokens, the empty string should be returned -- which is then interpreted as true value.

Therefore, 'zero_tokens' makes sense exclusively when the validator for the type handles empty string or 'implied_value' is also specified. Seems like purely documentation bug to me, then.

calum.mitchell@… — Wed, 29 Dec 2010 20:38:05 GMT

I ran into this problem when reading the documentation for 1.45.0 and trying to compile/run the example code.

The resolution appears to be:

desc.add_options()

("help", "produce help message")
("compression", value<string>(), "compression level")
("verbose", value<string>()->implicit_value("0"), "verbosity level")
("email", value<vector<string>>()->multitoken(), "email to send to")
;

As mentioned in an earlier comment, the use of value<vector<string>>() for a multitoken() option means that the option can occur more than one time on the command line.

status changed; resolution set

Vladimir Prus — Sat, 08 Jan 2011 11:45:55 GMT

status new → closed
resolution → fixed

(In [67774]) Clarify docs for 'zero_token'. Fixes #1132.