adding mutable lambdas action

Ok, I plan want to contribute to write csv or json parser in the examples, however sometime it was not comfortable since we cannot write some thing like following

auto syntax = R"(
    ROOT  <- _ TOKEN (',' _ TOKEN)*
    TOKEN <- < [a-z0-9]+ > _

    _     <- [ \t\r\n]*
)";

tree<string> sym ;
peg pg(syntax); 
pg["TOKEN"] = [=](const char* s, size_t l, const vector<any>& v){ //this will trigger an error because we need mutable lambdas, at peglib.h:273 and 276 didnt allow this
   sym.insert(sym.begin(),string(s,l));
   return string(s,l);
}

also this is useful for generating ast, or let user managing data structure. I have an Idea that, peg grammar is quite powerful to handle some ebnf with some restriction on how prioritization should be used.

[yhirose]

also this is useful for generating ast, or let user managing data structure. I have an Idea that, peg grammar is quite powerful to handle some ebnf with some restriction on how prioritization should be used.

Could you make another issue ticket for the suggestions to show your idea? I probably don't have time to work on the requests right now, but I'll ponder over the features and get back with you later.

Thanks!!

Hi thanks for adding this feature, here is working csv parser and sorry paste-ing here

/*
csv.cc
MIT License kangjoni76@gmail.com
*/
#include <peglib.h>
#include <iostream>
#include <cstdlib>
#include <vector>
#include <cctype>
#include <fstream>

int col,row;
std::vector<std::string> a;
void push(std::string m){

    a.push_back(m);
}
void failClue(int col){
std::cout << "failed at col "<<col<<" row "<<row<<"\nError token:";
    for (int ss=0;ss<a.size();++ss){
        std::cout << a.at(ss);
    }
    std::cout <<std::endl; 
    for (int c=0;c<col;++c){
        std::cout <<" ";
        if (c==(col-1)){
            std::cout <<"^";
        }
    }
}
int main(int argc, const char** argv)
{

 if (argc < 2 || std::string("--help") == argv[1]) {
        std::cout << "usage: "<<argv[0]<<" [input]" << std::endl;
        return 1;
    }
    std::string line,content;
    std::ifstream file(argv[1]); 
    auto syntax = R"(
    FILE <- HDR ROW+
    HDR <- ROW 
    ROW <- QUOTED STRING QUOTED  (COMMA   QUOTED STRING QUOTED)* _?
    _     <-  ' ' / '\t' / '\r' / [ \t\r\n]+
    STRING <- < [ a-z,-_.A-Z0-9]+ > 
    COMMA <- ','
    QUOTED <- '"'
)";
row=0;
peglib::peg pg(syntax); 
pg["FILE"] = []( const std::vector<peglib::any>& v){  
};
pg["ROW"] = [](const char *s,size_t l, const std::vector<peglib::any>& v) mutable{  
    ++row;
    col=l;
    push(std::string(s,l));
};
    if (!file.is_open()) {
        perror("error while opening file");  file.close();
    }
    while(std::getline(file, line)) {
        content+=line;
    }

auto ret = pg.parse(content.c_str()); 
std::cout <<std::boolalpha << ret<<"\n";
if (!ret){ 
    failClue(col);
}
file.close();
return 0;
}

file.csv

"04.1.00003","Da2d3d1,2","DAD.02"
"04.2.00003","D a2d3d12","DAD_.,0-3"
"04.3.00003","Da2d 3d1,2","DAD02"

I hope this can be useful for other poeple for starting point.

[yhirose]

Thanks for the code. It could be helpful for others. I have a request to improve the code.
Is it possible for you to fully support the CSV file format defined in RFC 4180 (http://www.ietf.org/rfc/rfc4180.txt)? Most CSV parsers in the world support the format.

I have actually wrote the PEG grammar based on the RFC 4180 format at csv.peg. You could use it in your code.

I appreciate your help!!

great, you just add hex number support. thanks