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

Subject: Re: [Boost-users] Boost.Spirit Karma: debug() alters result
From: Hartmut Kaiser (hartmut.kaiser_at_[hidden])
Date: 2016-03-04 10:48:39

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
---------------
http://boost-spirit.com
http://stellar.cct.lsu.edu

> -----Original Message-----
> From: Boost-users [mailto:boost-users-bounces_at_[hidden]] On Behalf
> Of Matwey V. Kornilov
> Sent: Friday, March 4, 2016 9:02 AM
> To: boost-users_at_[hidden]
> 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<Iterator, std::string()> {
> 
>         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<Iterator, std::string()> start;
>         karma::rule<Iterator, std::string()> value;
>         karma::rule<Iterator, std::string()> value1;
>         karma::rule<Iterator, std::string()> value2;
> };
> template <class Iterator>
> struct test_generator2:
>         karma::grammar<Iterator, std::string()> {
> 
>         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<Iterator, std::string()> start;
>         karma::rule<Iterator, std::string()> value;
>         karma::rule<Iterator, std::string()> value1;
>         karma::rule<Iterator, std::string()> 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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