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• How do I lex this input?

  - by etheros

  I currently have a working, simple language implemented in Java using ANTLR. What I want to do is embed it in plain text, in a similar fashion to PHP. For example: Lorem ipsum dolor sit amet <% print('consectetur adipiscing elit'); %> Phasellus volutpat dignissim sapien. I anticipate that the resulting token stream would look something like: CDATA OPEN PRINT OPAREN APOS STRINGAPOS CPARENT SEMI CLOSE CDATA How can I achieve this, or is there a better way?

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• flex and bison: wrong output

  - by user2972227

  I am doing a homework using flex and bison to make a complex number calculator. But my program cannot give a correct output. .lex file: %option noyywrap %{ #include<stdio.h> #include<stdlib.h> #include "complex_cal.h" #define YYSTYPE complex #include "complex_cal.tab.h" void RmWs(char* str); %} /* Add your Flex definitions here */ /* Some definitions are already provided to you*/ ws [ \t]+ digits [0-9] number (0|[1-9]+{digits}*)\.?{digits}* im [i] complexnum {ws}*[-]*{ws}*{number}{ws}*[+|-]{ws}*{number}{ws}*{im}{ws}* op [-+*/()] %% {complexnum} {RmWs(yytext); sscanf(yytext,"%lf %lf",&(yylval.real),&(yylval.img)); return CNUMBER;} {ws} /**/ {op} return *yytext; %% /* function provided to student to remove */ /* all the whitespaces from a string. */ void RmWs(char* str){ int i=0,j=0; char temp[strlen(str)+1]; strcpy(temp,str); while (temp[i]!='\0'){ while (temp[i]==' '){i++;} str[j]=temp[i]; i++; j++; } str[j]='\0'; } .y file: %{ #include <stdio.h> #include <stdlib.h> #include "complex_cal.h" /* prototypes of the provided functions */ complex complex_add (complex, complex); complex complex_sub (complex, complex); complex complex_mul (complex, complex); complex complex_div (complex, complex); /* prototypes of the provided functions */ int yylex(void); int yyerror(const char*); %} %token CNUMBER %left '+' '-' %left '*' '/' %nonassoc '(' ')' %% /* start: Add your grammar rules and actions here */ complexexp: complexexp '+' complexexpmultidiv {$$=complex_add($1, $3);} | complexexp '-' complexexpmultidiv {$$=complex_sub($1, $3);} | complexexpmultidiv {$$.real=$1.real;$$.img=$1.img;} ; complexexpmultidiv: complexexpmultidiv '*' complexsimple {$$=complex_mul($1, $3);} | complexexpmultidiv '/' complexsimple {$$=complex_div($1, $3);} | complexsimple {$$.real=$1.real;$$.img=$1.img;} ; complexsimple: '(' complexexp ')' {$$.real=$2.real;$$.img=$2.img;} | '(' CNUMBER ')' {$$.real=$2.real;$$.img=$2.img;} ; /* end: Add your grammar rules and actions here */ %% int main(){ return yyparse(); } int yyerror(const char* s){ printf("%s\n", s); return 0; } /* function provided to do complex addition */ /* input : complex numbers c1, c2 */ /* output: nothing */ /* side effect : none */ /* return value: result of addition in c3 */ complex complex_add (complex c1, complex c2){ /* c1 + c2 */ complex c3; c3.real = c1.real + c2.real; c3.img = c1.img + c2.img; return c3; } /* function provided to do complex subtraction */ /* input : complex numbers c1, c2 */ /* output: nothing */ /* side effect : none */ /* return value: result of subtraction in c3 */ complex complex_sub (complex c1, complex c2){ /* c1 - c2 */ complex c3; c3.real = c1.real - c2.real; c3.img = c1.img - c2.img; return c3; } /* function provided to do complex multiplication */ /* input : complex numbers c1, c2 */ /* output: nothing */ /* side effect : none */ /* return value: result of multiplication in c3 */ complex complex_mul (complex c1, complex c2){ /* c1 * c2 */ complex c3; c3.real = c1.real*c2.real - c1.img*c2.img; c3.img = c1.img*c2.real + c1.real*c2.img; return c3; } /* function provided to do complex division */ /* input : complex numbers c1, c2 */ /* output: nothing */ /* side effect : none */ /* return value: result of c1/c2 in c3 */ complex complex_div (complex c1, complex c2){ /* c1 / c2 (i.e. c1 divided by c2 ) */ complex c3; double d; /*divisor calculation using the conjugate of c2*/ d = c2.real*c2.real + c2.img*c2.img; c3.real = (c1.real*c2.real + c1.img*c2.img)/d; c3.img = (c1.img*c2.real - c1.real*c2.img)/d; return c3; } .h file: #include <string.h> /* struct for holding a complex number */ typedef struct { double real; double img; } complex; /* define the return type of FLEX */ #define YYSTYPE complex Script for compiling the file: bison -d -v complex_cal.y flex -ocomplex_cal.lex.yy.c complex_cal.lex gcc -o complex_cal complex_cal.lex.yy.c complex_cal.tab.c ./complex_cal Some correct sample run of the program: input:(5+6i)*(6+1i) output:24.000000+41.000000i input:(7+8i)/(-3-4i)*(5+7i) output:-11.720000-14.040000i input:(7+8i)/((-3-4i)*(5+7i)) output:-0.128108+0.211351i But when I run this program, the program only give an output which is identical to my input. For example, when I input (5+6i)(6+1i), it just gives (5+6i)(6+1i). Even if I input any other things, for example, input "abc" it just gives "abc" and is not syntax error. I don't know where the problem is and I hope to know how to solve it.

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• distinguishing a string with flex

  - by haluk

  Hi, I need to tokenize some strings which will be splitted of according to operators like = and !=. I was successful using regex until the string has != operator. In my case, string was seperated into two parts, which is expected but ! mark is in the left side even it is part of given operator. Therefore, I believe that regex is not suitable for it and I want to benefit from lex. Since I do not have enough knowledge and experience with lex, I am not sure whether it fits my work or not. Basically, I am trying to do replace the right hand side of the operators with actual values from other data. Do you people think that can it be helpful for my case? Thanks.

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• why does this boost::spirit::qi rule not work?

  - by Tobias Langner

  I have a grammar that defines the following rules: constantValue = qi::token(ID_FLOAT) | qi::token(ID_INTEGER); postfixExpression = primaryExpression | (postfixExpression >> qi::token(ID_OPENBRACKET) >> qi::token(ID_INTEGER) >> qi::token(ID_CLOSEBRACKET)) | (postfixExpression >> qi::token(ID_DOT) >> qi::token(ID_IDENTIFIER)); primaryExpression = qi::token(ID_IDENTIFIER) | constantValue | (qi::token(ID_OPENPAREN) >> primaryExpression >> qi::token(ID_CLOSEPAREN)); ges = postfixExpression >> qi::eoi; and I want it to match the following strings: test[1] testident.ident and it should not match test[1.2] testident.5 but it fails to match the first 2 strings. The lexer constructor is as follows: custom_lexer() : identifier("[a-zA-Z_][a-zA-Z0-9_]*") , white_space("[ \\t\\n]+") , integer_value("[1-9][0-9]*") , hex_value("0[xX][0-9a-fA-F]+") , float_value("[0-9]*\\.[0-9]+([eE][+-]?[0-9]+)?") , float_value2("[0-9]+\\.([eE][+-]?[0-9]+)?") , punctuator("&>|\\*\\*|\\*|\\+|-|~|!|\\/|%|<<|>>|<|>|<=|>=|==|!=|\\^|&|\\||\\^\\^|&&|\\|\\||\\?|:|,")// [ ] ( ) . &> ** * + - ~ ! / % << >> < > <= >= == != ^ & | ^^ && || ? : , { using boost::spirit::lex::_start; using boost::spirit::lex::_end; this->self.add (identifier, ID_IDENTIFIER) /*(white_space, ID_WHITESPACE)*/ (integer_value, ID_INTEGER) (hex_value, ID_INTEGER) (float_value, ID_FLOAT) (float_value2, ID_FLOAT) ("\\(", ID_OPENPAREN) ("\\)", ID_CLOSEPAREN) ("\\[", ID_OPENBRACKET) ("\\]", ID_CLOSEBRACKET) ("\\.", ID_DOT) (punctuator, ID_PUNCTUATOR) ; this->self("WS") = white_space; } Why don't I get a match for the mentioned strings? Thank you Tobias

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• Flex build error

  - by incrediman

  I'm totally new to flex. I'm getting a build error when using flex. That is, I've generated a .c file using flex, and, when running it, am getting this error: 1>lextest.obj : error LNK2001: unresolved external symbol "int __cdecl isatty(int)" (?isatty@@YAHH@Z) 1>C:\...\lextest.exe : fatal error LNK1120: 1 unresolved externals here is the lex file I'm using (grabbed from here): /*** Definition section ***/ %{ /* C code to be copied verbatim */ #include <stdio.h> %} /* This tells flex to read only one input file */ %option noyywrap %% /*** Rules section ***/ /* [0-9]+ matches a string of one or more digits */ [0-9]+ { /* yytext is a string containing the matched text. */ printf("Saw an integer: %s\n", yytext); } . { /* Ignore all other characters. */ } %% /*** C Code section ***/ int main(void) { /* Call the lexer, then quit. */ yylex(); return 0; } As well, why do I have to put a 'main' function in the lex syntax code? What I'd like is to be able to call yylex(); from another c file.

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• Flex/bison, error: undeclared

  - by Imran

  hallo, i have a problem, the followed program gives back an error, error:: Undeclared(first use in function), why this error appears all tokens are declared, but this error comes, can anyone help me, here are the lex and yac files.thanks lex: %{ int yylinenu= 1; int yycolno= 1; %} %x STR DIGIT [0-9] ALPHA [a-zA-Z] ID {ALPHA}(_?({ALPHA}|{DIGIT}))*_? GROUPED_NUMBER ({DIGIT}{1,3})(\.{DIGIT}{3})* SIMPLE_NUMBER {DIGIT}+ NUMMER {GROUPED_NUMBER}|{SIMPLE_NUMBER} %% <INITIAL>{ [\n] {++yylinenu ; yycolno=1;} [ ]+ {yycolno=yycolno+yyleng;} [\t]+ {yycolno=yycolno+(yyleng*8);} "*" {return MAL;} "+" {return PLUS;} "-" {return MINUS;} "/" {return SLASH;} "(" {return LINKEKLAMMER;} ")" {return RECHTEKLAMMER;} "{" {return LINKEGESCHWEIFTEKLAMMER;} "}" {return RECHTEGESCHEIFTEKLAMMER;} "=" {return GLEICH;} "==" {return GLEICHVERGLEICH;} "!=" {return UNGLEICH;} "<" {return KLEINER;} ">" {return GROSSER;} "<=" {return KLEINERGLEICH;} ">=" {return GROSSERGLEICH;} "while" {return WHILE;} "if" {return IF;} "else" {return ELSE;} "printf" {return PRINTF;} ";" {return SEMIKOLON;} \/\/[^\n]* { ;} {NUMMER} {return NUMBER;} {ID} {return IDENTIFIER;} \" {BEGIN(STR);} . {;} } <STR>{ \n {++yylinenu ;yycolno=1;} ([^\"\\]|"\\t"|"\\n"|"\\r"|"\\b"|"\\\"")+ {return STRING;} \" {BEGIN(INITIAL);} } %% yywrap() { } YACC: %{ #include stdio.h> #include string.h> #include "lex.yy.c" void yyerror(char *err); int error=0,linecnt=1; %} %token IDENTIFIER NUMBER STRING COMMENT PLUS MINUS MAL SLASH LINKEKLAMMER RECHTEKLAMMER LINKEGESCHWEIFTEKLAMMER RECHTEGESCHEIFTEKLAMMER GLEICH GLEICHVERGLEICH UNGLEICH GROSSER KLEINER GROSSERGLEICH KLEINERGLEICH IF ELSE WHILE PRINTF SEMIKOLON %start Stmts %% Stmts : Stmt {puts("\t\tStmts : Stmt");} |Stmt Stmts {puts("\t\tStmts : Stmt Stmts");} ; //NEUE REGEL---------------------------------------------- Stmt : LINKEGESCHWEIFTEKLAMMER Stmts RECHTEGESCHEIFTEKLAMMER {puts("\t\tStmt : '{' Stmts '}'");} |IF LINKEKLAMMER Cond RECHTEKLAMMER Stmt {puts("\t\tStmt : '(' Cond ')' Stmt");} |IF LINKEKLAMMER Cond RECHTEKLAMMER Stmt ELSE Stmt {puts("\t\tStmt : '(' Cond ')' Stmt 'ELSE' Stmt");} |WHILE LINKEKLAMMER Cond RECHTEKLAMMER Stmt {puts("\t\tStmt : 'PRINTF' Expr ';'");} |PRINTF Expr SEMIKOLON {puts("\t\tStmt : 'PRINTF' Expr ';'");} |IDENTIFIER GLEICH Expr SEMIKOLON {puts("\t\tStmt : 'IDENTIFIER' '=' Expr ';'");} |SEMIKOLON {puts("\t\tStmt : ';'");} ;//NEUE REGEL --------------------------------------------- Cond: Expr GLEICHVERGLEICH Expr {puts("\t\tCond : '==' Expr");} |Expr UNGLEICH Expr {puts("\t\tCond : '!=' Expr");} |Expr KLEINER Expr {puts("\t\tCond : '<' Expr");} |Expr KLEINERGLEICH Expr {puts("\t\tCond : '<=' Expr");} |Expr GROSSER Expr {puts("\t\tCond : '>' Expr");} |Expr GROSSERGLEICH Expr {puts("\t\tCond : '>=' Expr");} ;//NEUE REGEL -------------------------------------------- Expr:Term {puts("\t\tExpr : Term");} |Term PLUS Expr {puts("\t\tExpr : Term '+' Expr");} |Term MINUS Expr {puts("\t\tExpr : Term '-' Expr");} ;//NEUE REGEL -------------------------------------------- Term:Factor {puts("\t\tTerm : Factor");} |Factor MAL Term {puts("\t\tTerm : Factor '*' Term");} |Factor SLASH Term {puts("\t\tTerm : Factor '/' Term");} ;//NEUE REGEL -------------------------------------------- Factor:SimpleExpr {puts("\t\tFactor : SimpleExpr");} |MINUS SimpleExpr {puts("\t\tFactor : '-' SimpleExpr");} ;//NEUE REGEL -------------------------------------------- SimpleExpr:LINKEKLAMMER Expr RECHTEKLAMMER {puts("\t\tSimpleExpr : '(' Expr ')'");} |IDENTIFIER {puts("\t\tSimpleExpr : 'IDENTIFIER'");} |NUMBER {puts("\t\tSimpleExpr : 'NUMBER'");} |STRING {puts("\t\tSimpleExpr : 'String'");} ;//ENDE ------------------------------------------------- %% void yyerror(char *msg) { error=1; printf("Line: %d , Column: %d : %s \n", yylinenu, yycolno,yytext, msg); } int main(int argc, char *argv[]) { int val; while(yylex()) { printf("\n",yytext); } return yyparse(); }

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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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• Flex, continuous scanning stream (from socket). Did I miss something using yywrap()?

  - by Diederich Kroeske

  Working on a socketbased scanner (continuous stream) using Flex for pattern recognition. Flex doesn't find a match that overlaps 'array bounderies'. So I implemented yywrap() to setup new array content as soon yylex() detects < (it will call yywrap). No success so far. Basically (for pin-pointing my problem) this is my code: %{ #include <stdio.h> #include <string.h> #include <stdlib.h> #define BUFFERSIZE 26 /* 0123456789012345678901234 */ char cbuf1[BUFFERSIZE] = "Hello everybody, lex is su"; // Warning, no '\0' char cbuf2[BUFFERSIZE] = "per cool. Thanks! "; char recvBuffer[BUFFERSIZE]; int packetCnt = 0; YY_BUFFER_STATE bufferState1, bufferState2; %} %option nounput %option noinput %% "super" { ECHO; } . { printf( "%c", yytext[0] );} %% int yywrap() { int retval = 1; printf(">> yywrap()\n"); if( packetCnt <= 0 ) // Stop after 2 { // Copy cbuf2 into recvBuffer memcpy(recvBuffer, cbuf2, BUFFERSIZE); // yyrestart(NULL); // ?? has no effect // Feed new data to flex bufferState2 = yy_scan_bytes(recvBuffer, BUFFERSIZE); // packetCnt++; // Tell flex to resume scanning retval = 0; } return(retval); } int main(void) { printf("Lenght: %d\n", (int)sizeof(recvBuffer)) ; // Copy cbuf1 into recvBuffer memcpy(recvBuffer, cbuf1, BUFFERSIZE); // packetCnt = 0; // bufferState1 = yy_scan_bytes(recvBuffer, BUFFERSIZE); // yylex(); yy_delete_buffer(bufferState1); yy_delete_buffer(bufferState2); return 0; } This is my output: dkmbpro:test dkroeske$ ./text Lenght: 26 Hello everybody, lex is su>> yywrap() per cool. Thanks! >> yywrap() So no match on 'super'. According to the doc the lexxer is not 'reset' between yywrap's. What do I miss? 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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• 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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• 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 install Perl's Parse::Lex for ActivePerl?

  - by Nano HE

  Hi I am using ActivePerl 5.10.1 on Win XP. I can't find Lex package from the PPM list. Can I install other package to enable Parse::Lex?

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• error in coding a lexer in c

  - by mekasperasky

  #include<stdio.h> #include<ctype.h> #include<string.h> /* this is a lexer which recognizes constants , variables ,symbols, identifiers , functions , comments and also header files . It stores the lexemes in 3 different files . One file contains all the headers and the comments . Another file will contain all the variables , another will contain all the symbols. */ int main() { int i=0,j,k,count=0; char a,b[100],c[10000],d[100]; memset ( d, 0, 100 ); j=30; FILE *fp1,*fp2; fp1=fopen("source.txt","r"); //the source file is opened in read only mode which will passed through the lexer fp2=fopen("lext.txt","w"); //now lets remove all the white spaces and store the rest of the words in a file if(fp1==NULL) { perror("failed to open source.txt"); //return EXIT_FAILURE; } i=0; k=0; while(!feof(fp1)) { a=fgetc(fp1); if(a!=' '&&a!='\n') { if (!isalpha(a)) { switch(a) { case '+':{fprintf(fp2,"+ ----> PLUS \n"); i=0;break;} case '-':{fprintf(fp2,"- ---> MINUS \n"); i=0;break;} case '*':{fprintf(fp2, "* --->MULT \n"); i=0;break;} case '/':{fprintf(fp2, "/ --->DIV \n"); i=0;break;} //case '+=':fprintf(fp2, "%.20s\n", "ADD_ASSIGN"); //case '-=':fprintf(fp2, "%.20s\n", "SUB_ASSIGN"); case '=':{fprintf(fp2, "= ---> ASSIGN \n"); i=0;break;} case '%':{fprintf(fp2, "% ---> MOD \n"); i=0;break;} case '<':{fprintf(fp2, "< ---> LESSER_THAN \n"); i=0;break;} case '>':{fprintf(fp2, "> --> GREATER_THAN \n"); i=0;break;} //case '++':fprintf(fp2, "%.20s\n", "INCREMENT"); //case '--':fprintf(fp2, "%.20s\n", "DECREMENT"); //case '==':fprintf(fp2, "%.20s\n", "ASSIGNMENT"); case ';':{fprintf(fp2, "; --->SEMI_COLUMN \n"); i=0;break;} case ':':{fprintf(fp2, ": --->COLUMN \n"); i=0;break;} case '(':{fprintf(fp2, "( --->LPAR \n"); i=0;break;} case ')':{fprintf(fp2, ") --->RPAR \n"); i=0;break;} case '{':{fprintf(fp2, "{ --->LBRACE \n"); i=0;break;} case '}':{fprintf(fp2, "} ---> RBRACE \n"); i=0;break;} } } else { d[i]=a; //printf("%c\n",d[i]); i=i+1; } //} /* we can make the lexer more complex by including even more depths of checks for the symbols*/ } else { d[i+1]='\0'; printf("\n"); if((strcmp(d,"if ")==0)){fprintf(fp2,"if ----> IDENTIFIER \n"); //printf("%s \n",d); memset ( d, 0, 100 ); //printf("%s \n",d); count=count+1;} else if(strcmp(d,"then")==0){fprintf(fp2,"then ----> IDENTIFIER \n"); count=count+1;} else if(strcmp(d,"else")==0){fprintf(fp2,"else ----> IDENTIFIER \n"); count=count+1;} else if(strcmp(d,"switch")==0){fprintf(fp2,"switch ----> IDENTIFIER \n"); count=count+1;} else if(strcmp(d,"printf")==0){fprintf(fp2,"prtintf ----> IDENTIFIER \n"); count=count+1;} else if(strcmp(d,"scanf")==0){fprintf(fp2,"scanf ----> IDENTIFIER \n"); count=count+1;} else if(strcmp(d,"NULL")==0){fprintf(fp2,"NULL ----> IDENTIFIER \n"); count=count+1;} else if(strcmp(d,"int")==0){fprintf(fp2,"INT ----> IDENTIFIER \n"); count=count+1;} else if(strcmp(d,"char")==0){fprintf(fp2,"char ----> IDENTIFIER \n"); count=count+1;} else if(strcmp(d,"float")==0){fprintf(fp2,"float ----> IDENTIFIER \n"); count=count+1;} else if(strcmp(d,"long")==0){fprintf(fp2,"long ----> IDENTIFIER \n"); count=count+1;} else if(strcmp(d,"double")==0){fprintf(fp2,"double ----> IDENTIFIER \n"); count=count+1;} else if(strcmp(d,"const")==0){fprintf(fp2,"const ----> IDENTIFIER \n"); count=count+1;} else if(strcmp(d,"continue")==0)fprintf(fp2,"continue ----> IDENTIFIER \n"); else if(strcmp(d,"size of")==0){fprintf(fp2,"size of ----> IDENTIFIER \n"); count=count+1;} else if(strcmp(d,"register")==0){fprintf(fp2,"register ----> IDENTIFIER \n"); count=count+1;} else if(strcmp(d,"short")==0){fprintf(fp2,"short ----> IDENTIFIER \n"); count=count+1;} else if(strcmp(d,"auto")==0){fprintf(fp2,"auto ----> IDENTIFIER \n"); count=count+1;} else if(strcmp(d,"while")==0){fprintf(fp2,"while ----> IDENTIFIER \n"); count=count+1;} else if(strcmp(d,"do")==0){fprintf(fp2,"do ----> IDENTIFIER \n"); count=count+1;} else if(strcmp(d,"case")==0){fprintf(fp2,"case ----> IDENTIFIER \n"); count=count+1;} else if (isdigit(d[i])) { fprintf(fp2,"%s ---->NUMBER",d); } else if (isalpha(a)) { fprintf(fp2,"%s ----> Variable",d); //printf("%s",d); // memset ( d, 0, 100 );} //fprintf(fp2, "s\n", b); i=0; k=k+1; continue; } i=i+1; k=k+1; } fclose(fp1); fclose(fp2); printf("%d",count); return 0; } In this code , my source.txt has if (a+b) stored . But only ( , + and ) is getting written into lext.txt and not the identifier if or the variable a and b . Any particular reason why?

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• what should be the output of a lexer be in c?

  - by mekasperasky

  #include<stdio.h> int main() { int a,b; a=a+b; printf("%d",a); return 0; } what should be the output if this code is passed through a lexer

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• what should the output of a lexer be in c?

  - by mekasperasky

  #include<stdio.h> int main() { int a,b; a=a+b; printf("%d",a); return 0; } what should be the output if this code is passed through a lexer

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• expected identifier or '(' before '{' token in Flex

  - by user1829177

  I am trying to use Flex to parse 'C' source code. Unfortunately I am getting the error "expected identifier or '(' before '{' token" on lines 1,12,13,14... . Any ideas why? %{ %} digit [0-9] letter [a-zA-Z] number (digit)+ id (letter|_)(letter|digit|_)* integer (int) character (char) comma [,] %% {integer} {return INT;} {character} {return CHAR;} {number} {return NUM;} {id} {return IDENTIFIER;} {comma} {return ',';} [-+*/] {return *yytext;} . {} %% main() { yylex(); } The corresponding flex file is as shown below: %{ #include <ctype.h> #include <stdio.h> #include "myhead.h" #include "mini.l" #define YYSTYPE double # undef fprintf %} %token INT %token CHAR %token IDENTIFIER %token NUM %token ',' %left '+' '-' %left '*' '/' %right UMINUS %% lines:lines expr '\n' {printf("%g\n",$2);} |lines '\n' |D | ; expr :expr '*' expr {$$=$1*$3;} |expr '/' expr {$$=$1/$3;} |expr '+' expr {$$=$1+$3;} |expr '-' expr {$$=$1+$3;} |'(' expr ')' {$$=$2;} |'-' expr %prec UMINUS {$$=-$2;} |IDENTIFIER {} |NUM {} ; T :INT {} |CHAR {} ; L :L ',' IDENTIFIER {} |IDENTIFIER {} ; D :T L {printf("T is %g, L is %g",$1,$2);} ; %% /*void yyerror (char *s) { fprintf (stderr, "%s\n", s); } */ I am compiling the generated code using the command: gcc my_file.c -ly

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• Feed char array into stdin

  - by Brian Lindsey

  I am writing a parser for a mini scripting language. Some of my grammar rules require jumping to a different location in the file to obtain information. There doesn't seem to be a straightforward way to accomplish this. So, I was thinking about loading my data files into a char array array and parsing line by line. This will allow me to jump all over the array with ease. My question is, is it possible to feed char arrays (i.e. char *) into stdin, so I can easily invoke the yyparse() function as needed.

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• mysql-proxy got error which cause it to crash

  - by nonus25

  I got that message and i dont know what it is means: Oct 21 12:24:26 lex mysql-proxy: 2013-10-21 12:24:26: ((error)) last message repeated 98 times Oct 21 12:24:26 lex mysql-proxy: 2013-10-21 12:24:26: ((error)) network-mysqld-packet.c.596: COM_(0x04) should not be (OK|ERR|NULL), got: 00 Oct 21 12:24:26 lex kernel: [4163416.207121] mysql-proxy[14271] trap int3 ip:7ff96e8a4313 sp:7fffb9086ad0 error:0 Any idea what can be the cause of it ?

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• Humor in Documentation

  - by Lex Fridman

  Is a small amount of lighthearted wording or humor acceptable in source code documentation? For example, I have an algorithm that has a message hop around a graph (network) until its path forms a cycle. When this happens it is removed from the queue of the node it last resided on which removes it from memory. I write that in a comment, and finish the comment with "Rest in peace, little guy". That serves very little documenting purpose, but it cheers me up a bit, and I imagine it might cheer up other people I'm working with as they read through the code. Is this an acceptable practice, or should my in-code documentation resemble as much as possible the speeches of 2004 United States presidential candidate John Kerry? ;-)

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• Humor in Documentation

  - by Lex Fridman

  Is a small amount of lighthearted wording or humor acceptable in source code documentation? For example, I have an algorithm that has a message hop around a graph (network) until its path forms a cycle. When this happens it is removed from the queue of the node it last resided on which removes it from memory. I write that in a comment, and finish the comment with "Rest in peace, little guy". That serves very little documenting purpose, but it cheers me up a bit, and I imagine it might cheer up other people I'm working with as they read through the code. Is this an acceptable practice, or should my in-code documentation resemble as much as possible the speeches of 2004 presidential candidate John Kerry? ;-)

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• Is possible to write too many asserts?

  - by Lex Fridman

  I am a big fan of writing assert checks in C++ code as a way to catch cases during development that cannot possibly happen but do happen because of logic bugs in my program. This is a good practice in general. However, I've noticed that some functions I write (which are part of a complex class) have 5+ asserts which feels like it could potentially be a bad programming practice, in terms of readability and maintainability. I think it's still great, as each one requires me to think about pre- and post-conditions of functions and they really do help catch bugs. However, I just wanted to put this out there to ask if there is a better paradigms for catching logic errors in cases when a large number of checks is necessary.

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• Does Ubuntu ever push new versions of GCC into the package repository between releases?

  - by Lex Fridman

  Current version of GCC in Ubuntu 11.04 is 4.5.2. For certain C++0x features, I need GCC version 4.6, but would like to avoid compiling from source. Is there hope that Ubuntu will update GCC in the package repository before the next release in October (11.10). This question asks a similar thing except for an earlier version of Ubuntu and GCC. A second part of the question, if the answer is "no" to the first, then can I hope to see it appear in Ubuntu's unstable repository?

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• How to pronounce "std" as in "std::vector"

  - by Lex Fridman

  In C++, the STL (standard template library) includes a namespace std that contains the many data structures and algorithms that we all know and love. I've always pronounced this namespace just like sexually transmitted diseases: S T D. But then I listened to this excellent series of lectures by Stephan T. Lavavej and he pronounces it "stood". Which is the "correct" pronunciation or at least what is that most commonly used one?

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• LLVM-3.1 libLLVMSupport.a undefined reference to `dladdr'

  - by user91387

  I'm trying to compile using the llvm-3.1 package. I'm running 12.04 x64 (3.2.0-26 kernel) && 12.10 (3.5.0-4) x64 backported llvm-3.1 from quantal, then debian experimental. Next I tried 12.10 with the native ubuntu llvm-3.1 package; this failed as well. user@system:/tmp/llvm-test# make compiling cpp yacc file: decaf-llvm.y output file: decaf-llvm bison -b decaf-llvm -d decaf-llvm.y /bin/mv -f decaf-llvm.tab.c decaf-llvm.tab.cc flex -odecaf-llvm.lex.cc decaf-llvm.lex g++ -o ./decaf-llvm decaf-llvm.tab.cc decaf-llvm.lex.cc decaf-stdlib.c `llvm-config --cppflags --ldflags --libs core jit native` -ly -ll /usr/lib/llvm-3.1/lib/libLLVMSupport.a(Signals.o): In function `PrintStackTrace(void*)': (.text+0x6c): undefined reference to `dladdr' /usr/lib/llvm-3.1/lib/libLLVMSupport.a(Signals.o): In function `PrintStackTrace(void*)': (.text+0x18f): undefined reference to `dladdr' collect2: error: ld returned 1 exit status make: *** [decaf-llvm] Error 1 I know the code works as I've run it in centos fine using llvm-3.1-6.fc18(rpm) Google was a bit helpful with this: "On some systems, incluning Ubuntu 11.10, linking may fail with message that libLLVMSupport.a in function PrintStackTrace(void*) has undefined reference to dladdr." "Workaround is to compile LLVM with cmake specifying the following variable: -DCMAKE_EXE_LINKER_FLAGS=-ldl" http://svn.dsource.org/projects/bindings/trunk/llvm-3.0/Readme I double checked y ldflags and everything seems ok. user@system:/llvm-config --ldflags -L/usr/lib/llvm-3.1/lib -lpthread -lffi -ldl -lm I'm unclear of what to do next; any suggestions?

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• Last Grid Column Not Auto Resizing With Grid

  - by photo_tom

  I'm having a problem with my TextBoxs not "Auto" resizing. I'm trying to create a form that behaves and looks like the Properties Editor in Visual Studio. What appears to be happening is that the third column is not expanding to fill all of the available remaining space in the grid. Image below is how my form looks on startup. The width of the textboxs is determined by the MinWidth setting on the third ColumnDefinition statement. Also, the Width is set to "*". With any other setting, the resizing done with the GridSplitter doesn't work correctly. <StackPanel Orientation="Vertical" VerticalAlignment="Top" x:Name="Stacker" Grid.IsSharedSizeScope="True"> <Expander x:Name="Expand" IsExpanded="True" Header="This is a test of a Second Panel" Width="{Binding Width, ElementName=Stacker}"> <Grid x:Name="EditGrid1" Margin="3" > <Grid.RowDefinitions> <RowDefinition Height="Auto" /> <RowDefinition Height="Auto" /> <RowDefinition Height="Auto" /> <RowDefinition Height="Auto" /> <RowDefinition Height="Auto" /> <RowDefinition Height="Auto" /> <RowDefinition Height="Auto" /> </Grid.RowDefinitions> <Grid.ColumnDefinitions> <ColumnDefinition Width="Auto" MinWidth="50" SharedSizeGroup="SharedSize1" /> <ColumnDefinition Width="Auto" SharedSizeGroup="SharedSize2" /> <ColumnDefinition Width="*" MinWidth="50" x:Name="ValueCol" /> </Grid.ColumnDefinitions> <GridSplitter Grid.Column="1" x:Name="ToolBoxSplitter1" Grid.Row="1" Grid.RowSpan="6" Panel.ZIndex="1" HorizontalAlignment="Stretch" ResizeBehavior="PreviousAndNext" Width="3"/> <TextBlock MaxHeight="40" Grid.Column="0" Grid.Row="1" Text="{x:Static lex:DoSomeThingView.Name}" /> <TextBlock MaxHeight="40" Grid.Column="0" Grid.Row="2" Text="{x:Static lex:DoSomeThingView.Address}" /> <TextBlock MaxHeight="40" Grid.Column="0" Grid.Row="3" Text="{x:Static lex:DoSomeThingView.Zip}" /> <TextBlock MaxHeight="40" Grid.Column="0" Grid.Row="4" Text="{x:Static lex:DoSomeThingView.NumberOfDoors}" TextTrimming="CharacterEllipsis" Grid.IsSharedSizeScope="True" /> <TextBlock MaxHeight="40" Grid.Column="0" Grid.Row="5" Text="{x:Static lex:DoSomeThingView.DoubleNumber}" /> <TextBox Grid.Column="2" Grid.Row="1" x:Name="UserName1" MaxHeight="50" TextWrapping="Wrap" VerticalScrollBarVisibility="Auto" SpellCheck.IsEnabled="True" /> <TextBox Grid.Column="2" Grid.Row="2" x:Name="Address1" /> <TextBox Grid.Column="2" Grid.Row="3" x:Name="Zip1" /> <TextBox Grid.Column="2" Grid.Row="4" x:Name="NumberOfDoors1" /> <TextBox Grid.Column="2" Grid.Row="5" x:Name="DoubleNumber1" /> </Grid> </Expander> </StackPanel> Any suggestions on how to correct this?

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