lex

问题 Here is my lex file %% .|\n ECHO; %% How to run this program in windows? How to compile this? Please help me 回答1: Use this procedure to compile: How to compile LEX/YACC files on Windows? Basically: flex olex.l gcc lex.yy.c -o olex.exe And this modified file: %% .|"\n" { ECHO; } %% int yywrap(void) { return 0; } int main(void) { yylex(); return 0; } I hope this works for you. 来源： https://stackoverflow.com/questions/8373821/how-to-run-lex-file

问题 Closed. This question is off-topic. It is not currently accepting answers. Want to improve this question? Update the question so it's on-topic for Stack Overflow. Closed 6 years ago . In lex, I can define the following starting condition for equations defined between $...$ . %x EQN1 \$ { BEGIN(EQN1); } <EQN1>{ \$ { BEGIN(INITIAL); } [^\$]* {} } For equations between $$...$$ , how can I define the anything but $$ rule, such as in [^\$]* . I guess [^\$\$]* wouldn't work. 回答1: I think you don't

问题 I was wondering that in LEX, if i want to parse some code until a special symbol. For example: $display("Hello World"); Here, I want to get $display("Hello World") but except ; . I've already tried this: \$"display".*[^;] , it didn't seem to work. Any help will be appreciated. Thanks. 回答1: . matches any character, and the Kleene star * will match many of whatever precedes it. In this case, you're matching display followed by a list of any other character. That'll happen to include the bit you

问题 In the flex manual it mentions a "trailing context" pattern ( r/s ), which means r , but only if followed by s . However the following code doesn't compile (instead it gives an error of "unrecognized rule". Why? LITERAL a/b %% {LITERAL} { } 回答1: The simple answer is that unless you use the -l option, which is not recommended, you cannot put trailing context into a name definition. That's because flex: doesn't allow trailing context inside parentheses; and automatically surrounds expansions of

问题 The following two codes have been written in order to perform arithmetic operations on input , but it gives me syntax error all the time Here is the lex program %{ #include "y.tab.h" #include <stdlib.h> %} %% [0-9]+ {yylval = atoi(yytext);return ID;} [*-+/()] {return yytext[0];} '\n' {return END;} . {return yytext[0];} %% Here is the yacc program : %{ #include <stdio.h> #include <stdlib.h> #include "y.tab.h" %} %token ID END %% S: expr END { printf("Answer is : %d\n",$$); exit(1); } expr: ID

问题 How can I print the line number on which an error occurred. I tried using yylineno in the yyerror() function and writing %option yylineno in the .l file but after compiling it gives me an error " yylineno undeclared (first use in this function) " and if I initialize yylineno as 1 it gives me this error: error: redefinition of yylineno lex.yy.c:273: note: previous definition of yylineno was here 回答1: There is a second way to ask flex to provide the global variable yylineno: the command line

问题 I am using this windows version of flex (lex) and bison (yacc) to port my query compiler from linux to Windows. The output files, lex.yy.c , y.tab.c and y.tab.h are getting generated properly. However, I am getting the following link error. Error 29 error LNK2001: unresolved external symbol _yylval G:\Project\lex.yy.obj QC Error 30 error LNK1120: 1 unresolved externals G:\Project\QC.exe QC I tried copying the above files generated by the original linux versions of flex and yacc to Visual

问题 here the program counts the no of comment lines, single line comments and multi line comments and gives a total comments output with a file.txt as input file.txt //hellow world /*hello world1*/ /*hello world2 */ /*hello world3 hello world3.1*/ #include<> count.l %{ #include<stdio.h> #include<stdlib.h> int a=0,b=0,c=0,d; %} %% "//".* {a++;} "/*" {b++;} .*"*/" {b--;c++;} %% void main(int argc,char *argv[]){ yyin=fopen(argv[1],"r"); yylex(); printf("single line %d \nmultiline %d \n",a,c); d=a+c;

问题 Write a parser (both Yacc and Lex files) that uses the following productions and actions: S -> cSS {print “x”} S -> a {print “y”} S -> b {print “z”} Indicate the string that it will print when the input is cacba . I am getting this error: when I give input to it, it says valid input and also says syntax error. My Scanner Code is this %{ #include "prac.h" %} %% [c] {return C; } [a] {return A; } [b] {return B; } [ \t] ; \n { return 0; } . { return yytext[0]; } %% int yywrap(void) { return 1; }

问题 I'm attempting to create a boolean expression language/grammar for a personal project. The user will be able to write a string in a Java-like syntax, with provision for variables, which will be evaluated at a later time when the variables have been initialised. Rain For example, a user might enter the string @FOO+7 > 4*(5+@BAR); Later, when the variable FOO is initialised and equal to 6, and BAR is equal to 1, the expression evaluates to 13>24 and thus returns false. I'm using ANTLRworks to