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  • How To Compile YACC And LEX?

    - by nisha
    Actually I'm having YACC file as pos.yacc and LEX file name is pos1.lex.. while compilling I'm getting the folowing error... malathy@malathy:~$ cc lex.yy.c y.tab.c -ly -ll pos1.lex %{ #include "y.tab.h" int yylval; %} DIGIT [0-9]+ %% {DIGIT} {yylval=atoi(yytext);return DIGIT;} [\n ] {} . {return *yytext;} %% yacc file is pos.yacc %token DIGIT %% s:e {printf("%d\n",$1);} e:DIGIT {$$=$1;} |e e "+" {$$=$1+$2;} |e e "*" {$$=$1*$2;} |e e "-" {$$=$1-$2;} |e e "/" {$$=$1/$2;} ; %% main() { yyparse(); } yyerror() { printf("Error"); } so while compiling i m getting like malathy@malathy:~$ cc lex.yy.c y.tab.c -ly -ll pos.y: In function ‘yyerror’: pos.y:16: warning: incompatible implicit declaration of built-in function ‘printf’ pos.y: In function ‘yyparse’: pos.y:4: warning: incompatible implicit declaration of built-in function ‘printf’

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  • Sharing memory among YACC, Lex, and C files

    - by sczizzo
    I have a YACC (Bison) grammar, a Lex (Flex) tokenizer, and a C program among which I need to share a struct (or really any variable). Currently, I declare the actual object in the grammar file and extern it wherever I need it (which is to say, my C source file), usually using a pointer to manipulate it. I have a shared header (and implementation) file between the C file and the grammar file with functions useful for manipulating my data structure. This works, but it feels a little uncomfortable. Is there a better way to share memory between the grammar and program?

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  • Python: Trouble with YACC

    - by Rosarch
    I'm parsing sentences like: "CS 2310 or equivalent experience" The desired output: [[("CS", 2310)], ["equivalent experience"]] YACC tokenizer symbols: tokens = [ 'DEPT_CODE', 'COURSE_NUMBER', 'OR_CONJ', 'MISC_TEXT', ] t_DEPT_CODE = r'[A-Z]{2,}' t_COURSE_NUMBER = r'[0-9]{4}' t_OR_CONJ = r'or' t_ignore = ' \t' terms = {'DEPT_CODE': t_DEPT_CODE, 'COURSE_NUMBER': t_COURSE_NUMBER, 'OR_CONJ': t_OR_CONJ} for name, regex in terms.items(): terms[name] = "^%s$" % regex def t_MISC_TEXT(t): r'\S+' for name, regex in terms.items(): # print "trying to match %s with regex %s" % (t.value, regex) if re.match(regex, t.value): t.type = name return t return t (MISC_TEXT is meant to match anything not caught by the other terms.) Some relevant rules from the parser: precedence = ( ('left', 'MISC_TEXT'), ) def p_statement_course_data(p): 'statement : course_data' p[0] = p[1] def p_course_data(p): 'course_data : course' p[0] = p[1] def p_course(p): 'course : DEPT_CODE COURSE_NUMBER' p[0] = make_course(p[1], int(p[2])) def p_or_phrase(p): 'or_phrase : statement OR_CONJ statement' p[0] = [[p[1]], [p[3]]] def p_misc_text(p): '''text_aggregate : MISC_TEXT MISC_TEXT | MISC_TEXT text_aggregate | text_aggregate MISC_TEXT ''' p[0] = "%s %s" % (p[0], [1]) def p_text_aggregate_statement(p): 'statement : text_aggregate' p[0] = p[1] Unfortunately, this fails: # works as it should >>> token_list("CS 2110 or equivalent experience") [LexToken(DEPT_CODE,'CS',1,0), LexToken(COURSE_NUMBER,'2110',1,3), LexToken(OR_CONJ,'or',1,8), LexToken(MISC_TEXT,'equivalent',1,11), LexToken(MISC_TEXT,'experience',1,22)] # fails. bummer. >>> parser.parse("CS 2110 or equivalent experience") Syntax error in input: LexToken(MISC_TEXT,'equivalent',1,11) What am I doing wrong? I don't fully understand how to set precedence rules. Also, this is my error function: def p_error(p): print "Syntax error in input: %s" % p Is there a way to see which rule the parser was trying when it failed? Or some other way to make the parser print which rules its trying?

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  • Unintentional concatenation in Bison/Yacc grammar.

    - by troutwine
    I am experimenting with lex and yacc and have run into a strange issue, but I think it would be best to show you my code before detailing the issue. This is my lexer: %{ #include <stdlib.h> #include <string.h> #include "y.tab.h" void yyerror(char *); %} %% [a-zA-Z]+ { yylval.strV = yytext; return ID; } [0-9]+ { yylval.intV = atoi(yytext); return INTEGER; } [\n] { return *yytext; } [ \t] ; . yyerror("invalid character"); %% int yywrap(void) { return 1; } This is my parser: %{ #include <stdio.h> int yydebug=1; void prompt(); void yyerror(char *); int yylex(void); %} %union { int intV; char *strV; } %token INTEGER ID %% program: program statement EOF { prompt(); } | program EOF { prompt(); } | { prompt(); } ; args: /* empty */ | args ID { printf(":%s ", $<strV>2); } ; statement: ID args { printf("%s", $<strV>1); } | INTEGER { printf("%d", $<intV>1); } ; EOF: '\n' %% void yyerror(char *s) { fprintf(stderr, "%s\n", s); } void prompt() { printf("> "); } int main(void) { yyparse(); return 0; } A very simple language, consisting of no more than strings and integer and a basic REPL. Now, you'll note in the parser that args are output with a leading colon, the intention being that, when combined with the first pattern of the rule of the statement the interaction with the REPL would look something like this: > aaa aa a :aa :a aaa> However, the interaction is this: > aaa aa a :aa :a aaa aa aa > Why does the token ID in the following rule statement: ID args { printf("%s", $<strV>1); } | INTEGER { printf("%d", $<intV>1); } ; have the semantic value of the total input string, newline included? How can my grammar be reworked so that the interaction I intended?

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  • Filter y.output from bison or yacc?

    - by acidzombie24
    I am using bison and its difficult to figure out the conflicts by looking at y.output. Is there a tool to make or filter y.output so its more useful? i would love to see the full path to the state with the conflict but anything helpful is what i would like.

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  • Yacc and Lex inclusion confusion

    - by thejohnmeister
    I am wondering how to correctly compile a program with a Makefile that has calls to yyparse in it? This is what I do: I have a Makefile that compiles all my regular files and they have no connections to y.tab.c or lex.yy.c (Am I supposed to have them?) I do this on top of my code: #include "y.tab.c" #include "lex.yy.c" #include "y.tab.h" This is what happens when I try to make the program: When I just type in "make", it gives me many warnings. Some of the examples are shown below. In function yywrap': /src/parser.y:12: multiple definition ofyywrap' server.o :/src/parser.y:12: first defined here utils.o: In function yyparse': /src/y.tab.c:1175: multiple definition ofyyparse' server.o:/src/y.tab.c:1175: first defined here utils.o I get many different errors referring to different yy_* files. I have compiled successfully with multiple calls to yyparse in the past, but this time seems to be different. It seems an awful lot like an inclusion problem somewhere but I can't tell what it is. All my header files have ifndef conditions, as well. Thanks for your help!

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  • Python/YACC: Resolving a shift/reduce conflict

    - by Rosarch
    I'm using PLY. Here is one of my states from parser.out: state 3 (5) course_data -> course . (6) course_data -> course . course_list_tail (3) or_phrase -> course . OR_CONJ COURSE_NUMBER (7) course_list_tail -> . , COURSE_NUMBER (8) course_list_tail -> . , COURSE_NUMBER course_list_tail ! shift/reduce conflict for OR_CONJ resolved as shift $end reduce using rule 5 (course_data -> course .) OR_CONJ shift and go to state 7 , shift and go to state 8 ! OR_CONJ [ reduce using rule 5 (course_data -> course .) ] course_list_tail shift and go to state 9 I want to resolve this as: if OR_CONJ is followed by COURSE_NUMBER: shift and go to state 7 else: reduce using rule 5 (course_data -> course .) How can I fix my parser file to reflect this? Do I need to handle a syntax error by backtracking and trying a different rule?

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  • Python/YACC Lexer: Token priority?

    - by Rosarch
    I'm trying to use reserved words in my grammar: reserved = { 'if' : 'IF', 'then' : 'THEN', 'else' : 'ELSE', 'while' : 'WHILE', } tokens = [ 'DEPT_CODE', 'COURSE_NUMBER', 'OR_CONJ', 'ID', ] + list(reserved.values()) t_DEPT_CODE = r'[A-Z]{2,}' t_COURSE_NUMBER = r'[0-9]{4}' t_OR_CONJ = r'or' t_ignore = ' \t' def t_ID(t): r'[a-zA-Z_][a-zA-Z_0-9]*' if t.value in reserved.values(): t.type = reserved[t.value] return t return None However, the t_ID rule somehow swallows up DEPT_CODE and OR_CONJ. How can I get around this? I'd like those two to take higher precedence than the reserved words.

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  • How do I generate different yyparse functions from lex/yacc for use in the same program?

    - by th
    Hi, I want to generate two separate parsing functions from lex/yacc. Normally yacc gives you a function yyparse() that you can call when you need to do some parsing, but I need to have several different yyparses each associated with different lexers and grammars. The man page seems to suggest the -p (prefix) flag, but this didn't work for me. I got errors from gcc that indicated that yylval was not properly being relabeled (i.e. it claims that several different tokens are not defined). Does anyone know the general rpocedure for generating these separate functions? thanks

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  • how to parse from command line arguements in yacc ?

    - by user205688
    how to parse from command line arguements in yacc ? of course i undefined input in both lex & yacc and then wrote int input(void) { printf("in input\n:"); char c; if(target > limit) return 0; if((c = target[0][offset++]) != '\0') return (c); target++; offset =0; return (' '); } where target contains the command line arguements. But only the standard input is getting excueted how to make dis input function get executed.

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  • How to get entire input string in Lex and Yacc?

    - by DevDevDev
    OK, so here is the deal. In my language I have some commands, say XYZ 3 5 GGB 8 9 HDH 8783 33 And in my Lex file XYZ { return XYZ; } GGB { return GGB; } HDH { return HDH; } [0-9]+ { yylval.ival = atoi(yytext); return NUMBER; } \n { return EOL; } In my yacc file start : commands ; commands : command | command EOL commands ; command : xyz | ggb | hdh ; xyz : XYZ NUMBER NUMBER { /* Do something with the numbers */ } ; etc. etc. etc. etc. My question is, how can I get the entire text XYZ 3 5 GGB 8 9 HDH 8783 33 Into commands while still returning the NUMBERs? Also when my Lex returns a STRING [0-9a-zA-Z]+, and I want to do verification on it's length, should I do it like rule: STRING STRING { if (strlen($1) < 5 ) /* Do some shit else error */ } or actually have a token in my Lex that returns different tokens depending on length?

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  • How to fix a warning message associated with strlen() used in Yacc?

    - by user547894
    Hello! Please i need your help. Basically, I am facing this warning message upon compiling with gcc, and am not able to deduce the error: Here are the details: The warning message i am receiving is literrally as follows: y.tab.c: In function ‘yyparse’: y.tab.c:1317 warning: incompatible implicit declaration of built-in function ‘strlen’ My Lex File looks like: %{ #include <stdio.h> #include <stdlib.h> #include <ctype.h> #include "y.tab.h" void yyerror(const char*); char *ptrStr; %} %START nameState %% "Name:" { BEGIN nameState; } <nameState>.+ { ptrStr = (char *)calloc(strlen(yytext)+1, sizeof(char)); strcpy(ptrStr, yytext); yylval.sValue = ptrStr; return sText; } %% int main(int argc, char *argv[]) { if ( argc < 3 ) { printf("Two args are needed: input and output"); } else { yyin = fopen(argv[1], "r"); yyout = fopen(argv[2], "w"); yyparse(); fclose(yyin); fclose(yyout); } return 0; } My Yacc file is as follows: %{ #include <stdio.h> #include <stdlib.h> #include <ctype.h> #include "y.tab.h" void yyerror(const char*); int yywrap(); extern FILE *yyout; %} %union { int iValue; char* sValue; }; %token <sValue> sText %token nameToken %% StartName: /* for empty */ | sName ; sName: sText { fprintf(yyout, "The Name is: %s", $1); fprintf(yyout, "The Length of the Name is: %d", strlen($1)); } ; %% void yyerror(const char *str) { fprintf(stderr,"error: %s\n",str); } int yywrap() { return 1; } *I was wondering how to remove this warning message. Please any suggestions are highly appreciated! Thanks in advance.

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  • How do I get Bison/YACC to not recognize a command until it parses the whole string?

    - by chucknelson
    I have some bison grammar: input: /* empty */ | input command ; command: builtin | external ; builtin: CD { printf("Changing to home directory...\n"); } | CD WORD printf("Changing to directroy %s\n", $2); } ; I'm wondering how I get Bison to not accept (YYACCEPT?) something as a command until it reads ALL of the input. So I can have all these rules below that use recursion or whatever to build things up, which either results in a valid command or something that's not going to work. One simple test I'm doing with the code above is just entering "cd mydir mydir". Bison parses CD and WORD and goes "hey! this is a command, put it to the top!". Then the next token it finds is just WORD, which has no rule, and then it reports an error. I want it to read the whole line and realize CD WORD WORD is not a rule, and then report an error. I think I'm missing something obvious and would greatly appreciate any help - thanks! Also - I've tried using input command NEWLINE or something similar, but it still pushes CD WORD to the top as a command and then parses the extra WORD separately.

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  • identation control while developing a small python like language

    - by sap
    Hello, Im developing a small python like language using flex, byacc (for lexical and parsing) and C++, but i have a few questions regarding scope control. just as python it uses white spaces (or tabs) for identation, not only that but i want to implement index breaking like for instance if you type "break 2" inside a while loop thats inside another while loop it would not only break from the last one but from the first loop as well (hence the number 2 after break) and so on. example: while 1 while 1 break 2 end end #after break 2 it would jump right here but since i dont have an "anti" tab character to check when a scope ends (like C for example i would just use the '}' char) i was wondering if this method would the the best: i would define a global variable, like "int tabIndex" on my yacc file that i would access in my lex file using extern. then everytime i find a tab character on my lex file i would increment that variable by 1. when parsing on my yacc file if i find a "break" keyword i would decrement by the amount typed after it from the tabIndex variable, and when i reach and EOF after compiling and i get a tabIndex != 0 i would output compilation error. now the problem is, whats the best way to see if the identation got reduced, should i read \b (backspace) chars from lex and then reduce the tabIndex variable (when the user doesnt use break)? another method to achieve this? also just another small question, i want every executable to have its starting point on the function called start() should i hardcode this onto my yacc file? sorry for the long question any help is greatly appretiated. also if someone can provide an yacc file for python would be nice as a guideline (tried looking on google and had no luck). thanks in advance.

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  • Indentation control while developing a small python like language

    - by sap
    Hello, I'm developing a small python like language using flex, byacc (for lexical and parsing) and C++, but i have a few questions regarding scope control. just as python it uses white spaces (or tabs) for indentation, not only that but i want to implement index breaking like for instance if you type "break 2" inside a while loop that's inside another while loop it would not only break from the last one but from the first loop as well (hence the number 2 after break) and so on. example: while 1 while 1 break 2 'hello world'!! #will never reach this. "!!" outputs with a newline end 'hello world again'!! #also will never reach this. again "!!" used for cout end #after break 2 it would jump right here but since I don't have an "anti" tab character to check when a scope ends (like C for example i would just use the '}' char) i was wondering if this method would the the best: I would define a global variable, like "int tabIndex" on my yacc file that i would access in my lex file using extern. then every time i find a tab character on my lex file i would increment that variable by 1. when parsing on my yacc file if i find a "break" keyword i would decrement by the amount typed after it from the tabIndex variable, and when i reach and EOF after compiling and i get a tabIndex != 0 i would output compilation error. now the problem is, whats the best way to see if the indentation got reduced, should i read \b (backspace) chars from lex and then reduce the tabIndex variable (when the user doesn't use break)? another method to achieve this? also just another small question, i want every executable to have its starting point on the function called start() should i hardcode this onto my yacc file? sorry for the long question any help is greatly appreciated. also if someone can provide an yacc file for python would be nice as a guideline (tried looking on Google and had no luck). thanks in advance.

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  • I need to develop a parser. Can I use Lex and Yacc for the purpose?

    - by Scrooge
    I need to extract very particular data from log files(of different types and formats). Since I am a recent college passout; my mind ran to using Lex and Yacc for the purpose. Now I have the following Questions 1. Will it be legal to do so ? (This product I am working for belongs to one of the biggest tech companies in the world.) 2. Also ; I would like to know if I am being too afraid to write my own parser? 3. How can I use Lex and Yacc if my product is Windows based? Please tell me if you need any clarification or extra information.

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  • Tools to build a UI markup language parser

    - by Dan
    For a school project, I need to implement a parser for a (probably XML-based) markup language for User Interfaces. Based on the input it generates a HTML document with various UI components (textareas, inputs, panels, dialogs etc.) Do you have any suggestions for tools/libraries I might use for this? (At school we use Flex and Bison, but we're allowed to use modern tools -- maybe a tool that has the capabilities of both lex and yacc)

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  • I'm trying to ressurrect UnderC C/C++ interpreter [closed]

    - by Domingo
    Hello ! I'm trying to ressurrect UnderC C/C++ interpreter https://code.google.com/p/underc-fltk/ and I got it to compile with modern mingw compilers 3.4.5 and up, I need some experts advice on some topics: -Yacc/Bison grammar (example some problems with recognizing "unsigned" alone and "friend class") -ARM assembler only one function to call native os functions (X86 already there for windows and linux) -General improvements I expect it to work on WINCE, IPHONE, SYMBIAN in the near future. Thanks in advance for your expertize, time and attention !

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