option noyywrap bison-bridge bison-locations include stdio include std

%option noyywrap bison-bridge bison-locations
%{
#include < stdio .h >
#include < stdlib .h >

#define TAG_IDENT 1
#define TAG_NUMBER 2
#define TAG_CHAR 3
#define TAG_LPAREN 4
#define TAG_RPAREN 5
#define TAG_PLUS 6
#define TAG_MINUS 7 
#define TAG_MULTIPLY 8
#define TAG_DIVIDE 9

char *tag_names[] =
{
  "END_OF_PROGRAM" , "IDENT" , "NUMBER" ,
  "CHAR" , "LPAREN" , "RPAREN" , "PLUS" ,
  "MINUS" , "MULTIPLY" , "DIVIDE"
};

struct Position
{
  int line , pos , index;
};

void print_pos ( struct Position *p )
{
  printf("(%d,%d)" ,p->line, p->pos);
}

struct Fragment
{
  struct Position starting, following;
};

typedef struct Fragment YYLTYPE;

void print_frag ( struct Fragment *f )
{
  print_pos (&(f->starting));
  printf ("-");
  print_pos(&(f->following));
}

union Token {
    char *ident;
    long num;
    char ch;
};

typedef union Tokens YYSTYPE;

int continued;
struct Position cur;

#define YY_USER_ACTION\
{\
    int i;\
    if (! continued)\
        yylloc->starting = cur;\
    continued = 0;\

    for (i = 0; i < yyleng; i++)\
    {\
        if (yytext[i] == ’\n’)\
        {\
            cur.line++;\
            cur.pos = 1;\
        }\
        else\
            cur.pos++;\
        cur.index++;\
    }\

    yylloc->following = cur;\
}

void init_scanner(char *program)
{
  continued =0;
  cur.line = 1;
  cur.pos =1;
  cur.index = 0;
  yy_scan_string(program);
}

void err(char *msg)
{
  printf("Error ");
  print_pos(&cur);
  printf(": %s\n",msg);
}
%}

LETTER [a-zA-Z]
DIGIT [0-9]
IDENT {LETTER}({LETTER}|{DIGIT})*
NUMBER {DIGIT}+

%x COMMENTS CHAR_1 CHAR_2

%%
[\n\t ]+

\/\* BEGIN(COMMENTS); continued =1;
<COMMENTS>[~*]* continued =1;
<COMMENTS>\*\/ {
                print_frag(yylloc);
                printf(" comment\n");
                BEGIN(0);
              }
<COMMENTS>\*  continued =1;
<COMMENTS><<EOF>> {
                    err("end of program found, '*/' expected");
                    return 0;
                  }

\(  return TAG_LPAREN;
\)  return TAG_RPAREN;
\+  return TAG_PLUS;
-   return TAG_MINUS;
\*  return TAG_MULTIPLY;
\/  return TAG_DIVIDE;

{IDENT} {
    yylval - > ident = yytext;
    return TAG_IDENT;
  }

{NUMBER} {
  yylval - > num = atoi ( yytext );
  return TAG_NUMBER ;
  \’ 
  }

\’  BEGIN(CHAR_1); continued =1; 

. err("unexpected char");

<CHAR_1,CHAR_2>\n {
  err("newline in constant");
  BEGIN(0);
  yylval -> ch =0;
  return TAG_CHAR;
}

<CHAR_1>\\n yylval -> ch = '\n'; BEGIN(CHAR_2); continued =1;
<CHAR_1>\\\’ yylval -> ch = '\n'; BEGIN(CHAR_2); continued =1;
<CHAR_1>\\\\ yylval -> ch = '\n'; BEGIN(CHAR_2); continued =1;
<CHAR_1>\\. {
  err("unknown error");
  yylval -> ch =0;
  BEGIN(CHAR_2);
  continued =1;
}
<CHAR_1>\’ {
    err("empty");
    BEGIN(0);
    yylval->ch =0;
    return TAG_CHAR;
}

<CHAR_1>. yylval -> = yytext[0]; BEGIN(CHAR_2); continued =1;
<CHAR_2>\’ BEGIN(0); return TAG_CHAR;
<CHAR_2>[^\n\’]* err("to many chars"); continued =1;


%%

#define PROGRAM "/* Expression */ ( alpha + ’ beta ’ - ’\\n ’)\ n " \
" * 666666666 /* blah - blah - blah "

int main ()
{
  int tag;
  YYSTYPE value;
  YYLTYPE coords;
  init_scanner (PROGRAM);
  do
  {
    tag = yylex (&value ,&coords);
    if (tag != 0)
    { ... }
  }
  while ( tag != 0);
  return 0;
}