Re: First-class citizens with only one member causing trouble.

Hi Florian,

this reminds me of http://stackoverflow.com/questions/19823413/spirit-qi-attribute-propagation-issue-with-single-member-struct. I don't have an answer though.

Regarding your compiler implementation did you examine the mini-c example provided with qi? Inspiring.

Regards, Frank


Von meinem iPhone gesendet

> Am 31.07.2016 um 19:10 schrieb Florian Klemme <[email protected]>:
>
> I found another workaround I just don't understand. This works perfectly:
>
> // Instructions
> instruction = ( // Semicolon terminated instructions
>                 ( function_call
>                 | variable_declaration
>                 | variable_assignment
>                 | print_variable
>                 | print_text
>                 | scan_variable
>                 ) > ';')
>             // Non-semicolon terminated instructions
>             | if_else
>             | while_loop
>             | for_loop
>             | instruction_block;
>
> but this doesn't even compile:
>
> // Instructions
> instruction = (function_call        > ';')
>             | (variable_declaration > ';')
>             | (variable_assignment  > ';')
>             | (print_variable       > ';')
>             | (print_text           > ';')
>             | (scan_variable        > ';')
>             | if_else
>             | while_loop
>             | for_loop
>             | instruction_block;
>
>> On 29.07.2016 18:30, Florian Klemme wrote:
>> Hi,
>>
>> I have a little compiler project in which Spirit Qi works just fine. But there is one little change I'd like to accomplish that causes quite some (compilation) trouble. Have a look at this code snippet.
>>
>> // Instructions
>> instruction = (function_call        > ';')
>>             | (variable_declaration > ';')
>>             | (variable_assignment  > ';')
>>             | print_variable // Implicit semicolon TODO!!!?
>>             | print_text     // Implicit semicolon
>>             | scan_variable  // Implicit semicolon
>>             | if_else
>>             | while_loop
>>             | for_loop
>>             | instruction_block;
>>
>> function_call        = function_name >> '(' > -(variable_name % ',') > ')';
>> variable_declaration = qi::lexeme["var"] > variable_name > (('=' > expression) | qi::attr(expression::value_t{0u}));
>> variable_assignment  = variable_name >> '=' > expression;
>> print_variable       = qi::lexeme["print"] >> variable_name > ';';
>> print_text           = qi::lexeme["print"] >> qi::lexeme['"' > *(qi::char_ - '"') > '"'] > ';';
>> scan_variable        = qi::lexeme["scan"] > variable_name > ';';
>>
>> Don't look to deep into what these rules are composed of, the only thing that matters is that the first three rules have their trailing ';' defined in the instruction rule and the others have their ';' in the rule itself.
>>
>> I want to move all tailing ';' to the instruction rule as shown in the first few lines. For the first three rules this hasn't been a problem. The literal parser ';' doesn't affect the attribute of the rule so the position shouldn't matter.
>>
>> But in fact, appending any literal parser before any "// Implicit semicolon" comment causes a compilation error. It took me some time to figure out why this is not a problem with the other rules. It turns out the problem is that the attribute of the problematic three rules are first-class citizens with only one member (which happens to be a string, not sure if this is relevant).
>>
>> So the following ugly workaround actually leads to a compiling (and working) solution. By just adding a second member to the attribute of the rule.
>> diff --git a/bf/compiler.cpp b/bf/compiler.cpp
>> index 6f83c00..7cea53a 100644
>> --- a/bf/compiler.cpp
>> +++ b/bf/compiler.cpp
>> @@ -103,6 +103,7 @@ namespace instruction {
>>
>>      struct print_variable_t {
>>          std::string variable_name;
>> +        int         dummy;
>>      };
>>
>>      struct print_text_t {
>> @@ -253,7 +254,8 @@ BOOST_FUSION_ADAPT_STRUCT(
>>
>>  BOOST_FUSION_ADAPT_STRUCT(
>>          bf::instruction::print_variable_t,
>> -        (std::string, variable_name))
>> +        (std::string, variable_name)
>> +        (int,         dummy))
>>
>>  BOOST_FUSION_ADAPT_STRUCT(
>>          bf::instruction::print_text_t,
>> @@ -451,7 +453,7 @@ struct grammar : qi::grammar<iterator, program_t(), ascii::space_type> {
>>          instruction = (function_call        > ';')
>>                      | (variable_declaration > ';')
>>                      | (variable_assignment  > ';')
>> -                    | print_variable // Implicit semicolon TODO!!!?
>> +                    | (print_variable       > ';') // TODO!!!?
>>                      | print_text     // Implicit semicolon
>>                      | scan_variable  // Implicit semicolon
>>                      | if_else
>> @@ -462,7 +464,7 @@ struct grammar : qi::grammar<iterator, program_t(), ascii::space_type> {
>>          function_call        = function_name >> '(' > -(variable_name % ',') > ')';
>>          variable_declaration = qi::lexeme["var"] > variable_name > (('=' > expression) | qi::attr(expression::value_t{0u}));
>>          variable_assignment  = variable_name >> '=' > expression;
>> -        print_variable       = qi::lexeme["print"]             >> variable_name > ';';
>> +        print_variable       = qi::lexeme["print"]             >> variable_name > qi::attr(0);
>>          print_text           = qi::lexeme["print"]             >> qi::lexeme['"' > *(qi::char_ - '"') > '"'] > ';';
>>          scan_variable        = qi::lexeme["scan"] > variable_name > ';';
>>          if_else              = qi::lexeme["if"] > '(' > expression > ')' > instruction > -(qi::lexeme["else"] > instruction);
>> Have a look at https://github.com/Kruecke/BFGenerator if you want to check out the whole code. The critical section is this one: https://github.com/Kruecke/BFGenerator/blob/master/bf/compiler.cpp#L454. The workaround is committed in a branch as well: https://github.com/Kruecke/BFGenerator/compare/semicolon_workaround. If you want to run the code, make sure to run "make test" as the other rules don't compile this piece of code at the moment.
>> Please let me know if you have any idea how to fix this problem or what mistake I might have made. I am thankful for any ideas. Or is there a chance that this is a bug in Spirit Qi?
>>
>> I tested this with different versions of Boost as well as different versions of gcc and msvc. C++14 support is required.
>> Florian
>>
>>
>> ------------------------------------------------------------------------------
>>
>>
>> _______________________________________________
>> Spirit-general mailing list
>> [email protected]
>> https://lists.sourceforge.net/lists/listinfo/spirit-general
>

------------------------------------------------------------------------------

_______________________________________________
Spirit-general mailing list
[email protected]
https://lists.sourceforge.net/lists/listinfo/spirit-general