RE: Hi everyone,

[Jannick]

I think the following should fix the compile errors. Presumably they are 
prompted by compilers more sensitive nowadays than they were back in the days 
when this book was written:

- lexer.l: remove the declaration enum yytokentype which is shipped by 
including parser.tab.h
- parser.y: add forward declarations int yylex(void); and void yyerrror(char*); 
to, e.g., the section where headers are included.

Separately, you could drop '-lfl' from the compile statement in case you add

%option noyywrap

to the top of lexer.l.

I have not tested that, just from reading the code.

HTH
J.

On Sun, 17 Feb 2019 12:57:03 +0100, address@hidden wrote:
> I've managed to come a bit more forward, now my lexer.l files look like
> this:
> 
> %{
> #include <stdio.h>
> #include <stdlib.h>
> #include "./parser.tab.h"
> enum yytokentype {
>      NUMBER = 285,
>      VAL = 292,
>      ADD = 286,
>      SUB = 287,
>      MUL = 288,
>      DIV = 289,
>      ABS = 290,
>      EOL    = 291
> };
> int yylval;
> %}
> 
> %%
> 
> "+"            { return ADD; }
> "-"            { return SUB; }
> "*"            { return MUL; }
> "/"            { return DIV; }
> "|"            { return ABS; }
> [0-9]+        { yylval = atoi(yytext); return NUMBER; } \n            { 
> return EOL; } [
> \t]        { /* ignore whitespaces */ } .            { printf("Unknow char 
> :%c",
> *yytext); }
> 
> %%
> 
> 
> parser.y:
> 
> %{
> #include <stdio.h>
> #include <stdlib.h>
> %}
> 
> 
> %token NUMBER
> %token ADD SUB MUL DIV ABS
> %token EOL
> 
> %%
> 
> calclist: /* nothing */
>      | calclist exp EOL { printf(" = %d\n", $2); }
>      ;
> 
> exp: factor
>      | exp ADD factor { $$ = $1 + $3; }
>      | exp SUB factor { $$ = $1 - $3; }
>      ;
> 
> factor: term
>      | factor MUL term { $$ = $1 * $3; }
>      | factor DIV term { $$ = $1 / $3; }
>      ;
> 
> term: NUMBER
>      | ABS term { $$ = $2 >=0? $2 : - $2; }
>      ;
> 
> %%
> int main(int argc, char **argv){
>      yyparse();
>      return(0);
> }
> 
> int yyerror(char *s){
>      fprintf(stderr, "error: %s\n", s);
>      return(0);
> }
> 
> I can compile with flex -l lexer.l; bison -d parser.y; gcc -o parser 
> parser.tab.c
> lex.yy.c -lfl but i get the following error messages:
> 
> 
> parser.tab.c: In function ‘yyparse’:
> parser.tab.c:1124:16: warning: implicit declaration of function ‘yylex’
> [-Wimplicit-function-declaration]
>         yychar = yylex ();
>                  ^~~~~
> parser.tab.c:1289:7: warning: implicit declaration of function ‘yyerror’
> [-Wimplicit-function-declaration]
>         yyerror (YY_("syntax error"));
>         ^~~~~~~
> lexer.l:5:6: error: nested redefinition of ‘enum yytokentype’
>   enum yytokentype {
>        ^~~~~~~~~~~
> lexer.l:5:6: error: redeclaration of ‘enum yytokentype’
> In file included from lexer.l:4:0:
> ./parser.tab.h:46:8: note: originally defined here
>     enum yytokentype
>          ^~~~~~~~~~~
> lexer.l:6:2: error: redeclaration of enumerator ‘NUMBER’
>    NUMBER = 285,
>    ^~~~~~
> In file included from lexer.l:4:0:
> ./parser.tab.h:48:5: note: previous definition of ‘NUMBER’ was here
>       NUMBER = 258,
>       ^~~~~~
> lexer.l:8:2: error: redeclaration of enumerator ‘ADD’
>    ADD = 286,
>    ^~~
> In file included from lexer.l:4:0:
> ./parser.tab.h:49:5: note: previous definition of ‘ADD’ was here
>       ADD = 259,
>       ^~~
> lexer.l:9:2: error: redeclaration of enumerator ‘SUB’
>    SUB = 287,
>    ^~~
> In file included from lexer.l:4:0:
> ./parser.tab.h:50:5: note: previous definition of ‘SUB’ was here
>       SUB = 260,
>       ^~~
> lexer.l:10:2: error: redeclaration of enumerator ‘MUL’
>    MUL = 288,
>    ^~~
> In file included from lexer.l:4:0:
> ./parser.tab.h:51:5: note: previous definition of ‘MUL’ was here
>       MUL = 261,
>       ^~~
> lexer.l:11:2: error: redeclaration of enumerator ‘DIV’
>    DIV = 289,
>    ^~~
> In file included from lexer.l:4:0:
> ./parser.tab.h:52:5: note: previous definition of ‘DIV’ was here
>       DIV = 262,
>       ^~~
> lexer.l:12:2: error: redeclaration of enumerator ‘ABS’
>    ABS = 290,
>    ^~~
> In file included from lexer.l:4:0:
> ./parser.tab.h:53:5: note: previous definition of ‘ABS’ was here
>       ABS = 263,
>       ^~~
> lexer.l:13:2: error: redeclaration of enumerator ‘EOL’
>    EOL = 291
>    ^~~
> In file included from lexer.l:4:0:
> ./parser.tab.h:54:5: note: previous definition of ‘EOL’ was here
>       EOL = 264
>       ^~~
> 
> 
> 
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