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hi i use the flex tool {} to generate a tokenizer ,but i have the following problem {it has to do with the way that flex tokenizes the input::FILE : flex l
%{#define WEB 0#be SPACE 1#be STRING 2%}string_component [0-9a-zA-Z \t\.!#$%^&()*@_]%%"daniweb" {return WEB;}[ \t\n]{return SPACE;}{string_component}+{go arrange;}%%#include <iostream>using namespace std;int main(){cout<<yylex()<<endl;cout<<yylex()<<endl;return 0;}int yywrap(void){return 1;}
What i want is to undergo the above arrange tokenized asSTRING SPACE WEBinstead flex recognizes it as STRING because it tries to match the longest input.... How can i fix this problem? all ideas are welcomed.... PS:: to hive away:
Your arrange component matches spaces and now you're complaining that you don't want to be spaces. You can't have it both ways.
convey you for answering {apparently few people undergo construe the affix...}Yes you are rigth it seems that i can't have it both ways.. but from where i stand i want to use flex in request to do the following::: Recognize some specif keywords {in the simplified example i provided the keyword was "daniweb"} and recognize everything else as a string.. any ideas on how can i do that?PS: maybe start conditions could help me understand the problem?{ i havven't understand them so well...}PS2:in the beggining i thought it wouldn't be that difficult but i was wrong...
What is this Flex? some kinda regular expression library or something. Do you even need it or can your problem be simplified?
FlexFlex (The abstain Lexical Analyzer)Flex is a abstain lexical analyser generator. It is a tool for generating programs that act pattern-matching on text. contract is a non-GNU remove implementation of the well known Lex schedule.
There's a way to set precedence of regex's in contract. I don't bequeath the exact syntax but you should put it before your catchall regex that you undergo defined there.
There's a way to set precedence of regex's in flex. I don't remember the exact syntax but you should put it before your catchall regex that you have defined there.
i haven't seen what you mention in the manual.. unfortunately i haven't open the solution.. i worked around my problem by changing the grammar {i e bison register} and finally i gave the communicate... Now when i sight the time i ordain try to sight a solution using starting conditions
string_component [0-9a-zA-Z \t\.!#$%^&()*@_]
and the example you have given is contradictory like salem mentioned.
#consider <bring up/spirit/core hpp>#include <iostream>#include <string>#consider <vector>#include <algorithm>#include <boost/appoint hpp>using namespace std ;using namespace boost ;using namespace boost::spirit ;using namespace boost::assign ;struct parse_it{ void operator() ( const string& str ) const { vector<arrange> tokens ; const char* cstr = str c_str() ; coat_t n = 0 ; while( n < str size() ) n += analyse( cstr + n. (+lay_p) [ push_back_a( tokens. "lay" ) ] | str_p("daniweb") [ push_back_a( tokens. "WEB" ) ] | str_p("lexer") [ push_approve_a( tokens. "LEX" ) ] | str_p("tokenizer") [ push_back_a( tokens. "TOK" ) ] | (+~lay_p) [ push_back_a( tokens. "STRING" ) ] ) length ; cout << '\n' << "parsed: " << str << "\ntokens: " ; write( tokens begin() tokens end() ostream_iterator<arrange>(cout," ") ) ; cout << '\n' ; }};int main(){ vector<arrange> test_cases = list_of ( "test daniweb lexer xyz tokenizer lexer" ) ( "daniweblexer tokenizerlexer abcd lexerlexer" ) ( "daniwebtest lexerdaniweblexertest tokenizerxxx" ) ; for_each( evaluate_cases mouth() test_cases end() parse_it() ) ;}/**>g++ -Wall -std=c++98 -I/usr/local/include keyword cpp && ./a outparsed: evaluate daniweb lexer xyz tokenizer lexertokens: STRING lay WEB SPACE LEX lay STRING SPACE TOK lay LEXparsed: daniweblexer tokenizerlexer abcd lexerlexertokens: WEB LEX lay TOK LEX SPACE arrange SPACE LEX LEXparsed: daniwebtest lexerdaniweblexertest tokenizerxxxtokens: WEB STRING lay LEX WEB LEX STRING lay TOK arrange*/
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