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Extract tokens from grammar


Extract tokens from grammar

By : user2173202
Date : October 21 2020, 08:10 PM
it helps some times For the particular challenge you're solving, using a grammar is like using a sledgehammer to crack a nut.
Like @Scimon says, a single regex would be fine. You can keep it nicely readable by laying it out appropriately. You can name the captures and keep them all at the top level:
code :
/ ^
  '#' $<id>=(\d+) ' '
  '@ ' $<x>=(\d+) ',' $<y>=(\d+)
  ': ' $<w>=(\d+)  x  $<d>=(\d+)
  $
/;

say ~$<id x y w d>; # 1 1 3 4 4
say $match<id>.hash<digits>.<digit>; # [「1」]
say ~$match<id> # 1
say ~$match<coordinates><digits>[1] # 3
token coordinates { (<digits>) ',' (<digits>) }
say ~$match<coordinates>[1] # 3
token coordinates { $<x>=(<digits>) ',' $<y>=(<digits>) }

say ~$match<coordinates><y> # 3
my $made;
grammar Claim {
  token TOP {
    '#' <id> \s* '@' \s* <coordinates> ':' \s* <dimensions>
     { $made = ~($<id>, $<coordinatess><x y>, $<dimensions><digits>[0,1]) }
  }
...
say $made # 1 1 3 4 4
{ make ~($<id>, $<coordinatess><x y>, $<dimensions><digits>[0,1]) }
say $match.made # 1 1 3 4 4
say $match.ast # 1 1 3 4 4


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Boost spirit grammar rule to extract just alphanumeric tokens

Boost spirit grammar rule to extract just alphanumeric tokens


By : Robin Knodel
Date : March 29 2020, 07:55 AM
I think the issue was by ths following , I have a lexeme as below for words which are alhanumeric. , I'd literally write what you describe:
code :
    std::vector<std::wstring> parsed;
    bool ok = qi::phrase_parse(
            begin(input), end(input),
            *qi::lexeme [ +qi::alnum ],
            ~qi::alnum,
            parsed);
#include <boost/spirit/include/qi.hpp>

namespace qi = boost::spirit::qi;

int main()
{
    std::wstring input = L"STR1 + STR2 % STR3 () STR4 = STR5+ STR6";

    std::vector<std::wstring> parsed;
    bool ok = qi::phrase_parse(begin(input), end(input),
            *qi::lexeme [ +qi::alnum ],
            ~qi::alnum,
            parsed);

    for(auto& v : parsed)
        std::wcout << v << std::endl;
}
STR1
STR2
STR3
STR4
STR5
STR6
What do the ':!' and '|!' tokens mean in an (Python) Antlr grammar

What do the ':!' and '|!' tokens mean in an (Python) Antlr grammar


By : shubian jiang
Date : March 29 2020, 07:55 AM
it should still fix some issue I have inherited an old Antlr grammar which is used in a Python program. One of the productions looks like this: , :! and |! mean to not build AST for the surrounding rules.
What are the last four tokens of Python 3.5 grammar?

What are the last four tokens of Python 3.5 grammar?


By : SimpleMax
Date : March 29 2020, 07:55 AM
this will help token.OP
Is a generalization of the operator tokens. This is also mentioned in the tokenize module:
code :
/* Special definitions for cooperation with parser */
#define NT_OFFSET       256

#define ISTERMINAL(x)       ((x) < NT_OFFSET)
#define ISNONTERMINAL(x)    ((x) >= NT_OFFSET)
Antlr4: How can I both hide and use Tokens in a grammar

Antlr4: How can I both hide and use Tokens in a grammar


By : myno
Date : March 29 2020, 07:55 AM
this one helps. Found one way to handle this.
The idea is to divert EOL into one hidden channel and the other stuff I don´t want to see in another hidden channel (like spaces and comments). Then I use some code to backtrack the tokens when an EOL is supposed to show up and examine the previous tokens channels (since they already have been consumed). If I find something on EOL channel before I run into something from the ordinary channel, then it is ok.
code :
@lexer::members {
    public static int EOL_CHANNEL = 1;
    public static int OTHER_CHANNEL = 2;
}

...

EOL
  : '\r'? '\n'  ->  channel(EOL_CHANNEL)
  ;

LINE_SPACE
  : [ \t]+  ->  channel(OTHER_CHANNEL)
  ;
end_control_statment
  : END_STATEMENT
  | { isEOLPrevious() }?
  ;
@parser::members {
  public static int EOL_CHANNEL = 1;
  public static int OTHER_CHANNEL = 2;

  boolean isEOLPrevious()
  {
        int idx = getCurrentToken().getTokenIndex();
        int ch;

        do
        {
            ch = getTokenStream().get(--idx).getChannel();
        }
        while (ch == OTHER_CHANNEL);

        // Channel 1 is only carrying EOL, no need to check token itself
        return (ch == EOL_CHANNEL);
     }
}
How to get bison grammar rule for tokens

How to get bison grammar rule for tokens


By : user3000598
Date : March 29 2020, 07:55 AM
will help you Bison allows actions to be within a rule (known as mid-rule actions).
In your example they could be used like this:
code :
rule1 : TOKEN { printf("Found TOKEN 1\n"); } rule2 TOKEN { printf("Found TOKEN\n") ; }

rule2 : ATOKEN { printf("Found ATOKEN\n") ; }
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