%{
/*
**
**  samplec.l -- lexical analysia
**
*/

#ifdef      DEBUG

#  include <assert.h>

  main ()
    {
     char * p;

     assert(sizeof(int) >= sizeof(char *));

     while (p = (char *) yylex())
       printf("%-10.10s is "%s"n",p, yytext);
  }

  s_lookup() {}

  int yyerrs = 0;

#   define token(x) (int) "x"

#else ! DEBUG

#   define "y.tab.h"
#   define token(x) x

#endif DEBUG

#define END(v) (v-1 + sizeof v / sizeof v[0])
static int screen();
%}

letter                      [a-zA-Z]
digit                       [0-9]
letter_or_digit             [a-zA-Z0-9]
white_space         [ tn]
blank                       [ t]
other                       .

%%

^"#"{blank}*{digit}+({blank}+.*)?n yymark();

">="                    return token(GE);
"<="                        return token(LE);
"=="                        return token(EQ);
"!="                        return token(NE);
"+="                        return token(PE);
"-="                        return token(ME);
"*="                        return token(TE);
"/="                        return token(DE);
"%="                        return token(RE);
"++"                        return token(PP);
"--"                        return token(MM);

{letter}{letter_or_digit} return screen();

{digit}+            { s_lookup(token(Constant));
                          return token(Constant);
                    }

{white_space}*              ;

{other}                     return token(yytext[0]);

%%

/*
**
**  reserve word screening
**
*/

static struct rwtable {
    char *rw_name;
    int rw_yylex;
   } rwtable[] ={
   "break", token(BREAK),
   "continue", token(CONTINUE),
   "else", token(ELSE),
   "if", token(IF),
   "int", token(INT),
   "return", token(RETURN),
   "while", token(WHILE)
   };

static int screen()
   {
    struct rwtable * low = rwtable,
            * high = END(rwtable),
            * mid;

    int c;

    while (low <= high)
      {
       mid = low + (high-low)/2;
       if ((c = strcmp(mid->rw_name, yytext)) == 0)
            return mid->rw_yylex;
       else if (c < 0)
            low = mid+1;
       else
            high = mid-1;
     }
     s_lookup(token(Identifier));
     return token(Identifier);
}

#define token(x) (int) "x"

#define token(x) #x