Re: [Boost-users] Boost.Spirit Karma: debug() alters result

4 Mar 2016


      That looks like a bug, however I don't have an immediate solution for that.
I'll try to look into this as soon as I find some free time.

Regards Hartmut
---------------
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...
-----Original Message-----
From: Boost-users [mailto:boost-users-bounces@lists.boost.org] On Behalf
Of Matwey V. Kornilov
Sent: Friday, March 4, 2016 9:02 AM
To: boost-users@lists.boost.org
Subject: [Boost-users] Boost.Spirit Karma: debug() alters result
Hello,
I am using boost 1.58 and I see the following.
template <class Iterator>
struct test_generator:
        karma::grammar {
test_generator(): test_generator::base_type(start) {
                using karma::ascii::string;
                using boost::spirit::ascii::char_;
                using karma::lit;
                using karma::buffer;
                using karma::debug;
value2 = +(~char_(' '));
                value1 = value2;
                value = lit('=') << value1;
                start = buffer[-value];
        }
karma::rule start;
        karma::rule value;
        karma::rule value1;
        karma::rule value2;
};
template <class Iterator>
struct test_generator2:
        karma::grammar {
test_generator2(): test_generator2::base_type(start) {
                using karma::ascii::string;
                using boost::spirit::ascii::char_;
                using karma::lit;
                using karma::buffer;
                using karma::debug;
value2 = +(~char_(' '));
                value1 = value2;
                value = lit('=') << value1;
                debug(value);
                start = buffer[-value];
        }
karma::rule start;
        karma::rule value;
        karma::rule value1;
        karma::rule value2;
};
template<class It>
bool do_generate(It it, const std::string& x) {
        test_generator<It> g;
        return karma::generate(it, g, x);
}
template<class It>
bool do_generate2(It it, const std::string& x) {
        test_generator2<It> g;
        return karma::generate(it, g, x);
}
//...
std::string x2,x3;
        do_generate(std::back_inserter(x2), std::string(""));
        do_generate2(std::back_inserter(x3), std::string(""));
        std::cerr << "|" << x2 << "|" << std::endl;
        std::cerr << "|" << x3 << "|" << std::endl;
//...
The code prints:
<unnamed-rule>
  <try>
    <attributes>[[]]</attributes>
  </try>
  <fail/>
</unnamed-rule>
|=|
||
I.e. introduction of debug() alters result of the generator. Could you
please explain me where I am wrong? I am stuck now.
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Re: [Boost-users] Boost.Spirit Karma: debug() alters result

Hartmut Kaiser