C/C++ Interactive Guide/c-cplusplus-interactive-guide.iso/c_ref/csource3/173_01/cstock.lxi

Text File | 1979-12-31 | 5.6 KB | 217 lines

/*
 * Lexical Analyzer for C Library Driver
 *    - evaluates C chars, strings, ints, and floats
 *    - accepts unquoted chars and strings of printing characters
 */

ascii    = [\0-\177];          /* Any ASCII character */
white    = [\n\r\t ];          /* The white spaces */
sign     = [-+];               /* Numeric signs */
digit    = [0-9];              /* The digits */
hexdigit = [0-9A-Fa-f];        /* The hexadecimal digits */
hexflag  = [Xx];               /* Inidcator of a hexadecimal constant */
expflag  = [Ee];               /* Inidcator of a floating exponent */

t_atom = [!-~];                  /* All the printing characters */
text   = [!#-&(-/:-~](t_atom)*;  /* Text can't start with a digit, " or ' */

e_particle   = "\\" ascii;    /* An escaped ascii character */
s_particle   = [^\\"];        /* Anything besides an escape or a quote */
c_particle   = [^\\'];        /* Anything besides an escape or an apostrophe */

c_atom = e_particle | c_particle; /* Anything but end of char */
s_atom = e_particle | s_particle; /* Anything but end of string */

string = '"' s_atom*  '"';
char   = "'" c_atom*  "'";

%{
#include "std.h"
#include "clib.h"

TEXT yytext[100];
INTEGER yyival;
FLOAT yyfval, pow();
%}
%%

ARG               {return(ARG);}
PRINTF           {return(PTF);}
ISLOWER        {return(ILO);}
EXIT           {return(EXT);}

[-]*(digit)(hexflag)*(hexdigit)* {
       {register TEXT *p = yytext;
        BOOLEAN minus = FALSE;
        INTEGER base;

        gettoken(yytext, sizeof(yytext));
        yyival = 0;
        if(*p == '-') {
            ++p;
            minus = TRUE;
        }
        base = 10;
        if(*p == '0') {
            ++p;
            if(*p == 'X' || *p == 'x') {
                ++p;
                base = 16;
            } else
                base =  8;
        }
        do {
            yyival = base*yyival + hex(*p);
        } while(*++p);
        if(minus) yyival = -yyival;
        printf("\nLEX/ICON: %s is %d (decimal)\n", yytext, yyival);
        return(ICON);
        }}

[-]*(digit)*"."*(digit)*expflag*sign*digit* {{
        register TEXT *p = yytext;
        FLOAT divisor = 10.0, multiplier = 0.0;
        BOOLEAN minus = FALSE, expminus = FALSE;
        BOOLEAN decimal = FALSE, exponent = FALSE;

        gettoken(yytext, sizeof(yytext));
        yyfval = 0.0;
        if(*p == '-') {
            ++p;
            minus = TRUE;
        }

        do {
            switch(*p) {
            case '.': decimal = TRUE;
                      break;

            case 'e':
            case 'E': exponent = TRUE;
                      if(*(p+1) == '-' || *(p+1) == '+')
                            expminus = (*++p == '-') ? TRUE : FALSE;
                      break;

            default : if(!decimal && ! exponent) {
                          yyfval = 10. * (yyfval) + (*p - '0');
                          break;
                       } else if(!exponent) {
                          yyfval = yyfval + (*p - '0')/divisor;
                          divisor *= 10.;
                          break;
                       } else
                          multiplier = 10. * multiplier + (*p - '0');
            }
        } while (*++p);

            if(minus) yyfval = -yyfval;
            if(expminus) multiplier = -multiplier;
            if(exponent) yyfval = yyfval * pow(10., multiplier);
            printf("\nLEX/FCON: %s is %f\n", yytext, yyfval);
            return(FCON);
        }}

text  {
       gettoken(yytext, sizeof(yytext));
       if(strlen(yytext) == 1) {
           printf("\nLEX/CCON: '%s'\n", yytext);
           return(CCON);
       } else {
          printf("\nLEX/SCON: \"%s\"\n", yytext);
          return(SCON);
       }
      }

string  {
          gettoken(yytext, sizeof(yytext));
          strcpy(yytext, yytext+1);
          yytext[strlen(yytext)-1] = NULL;
          descape(yytext);
          printf("\nLEX/SCON: \"%s\"\n", yytext);
          return(SCON);
        }

char  {
       gettoken(yytext, sizeof(yytext));
       strcpy(yytext, yytext+1);
       yytext[strlen(yytext)-1] = NULL;
       descape(yytext);
       printf("\nLEX/CCON: '%s'\n", yytext);
       return(CCON);
      }

white(white)*    {return(LEXSKIP);}

%%

lexgetc(){
    static BOOLEAN newline = TRUE;
    register int c;

    if(newline)
        printf("%s>", "C Lib");

    if((c = getc(lexin)) == '\n')
        newline = TRUE;
    else
        newline = FALSE;

    return(c);
}

/*
** Translate escape sequences in a character string
*/
descape(str)
register STRING str;
{
        register STRING s;
        COUNT i;

        for(s = str; *str; s++, str++) {

            if(*str != '\\')
                *s = *str;
            else if (0 <= (i = ndex("'\"bnrtf", *++str)))
                *s = "'\"\b\n\r\t\f"[i];
            else if (isdigit(*str)) { register BYTE d;
                *s = *str - '0';
                for (i=0; (d = *(str+1)) && isdigit(d) && i < 3; i++, str++)
                        *s = (*s << 3) + d - '0';
            }
        }
        *s = '\0';
}

/*
** Find the index of a character in a string
*/
INTEGER ndex(str, chr)
register STRING str;
CHARACTER chr;
{
    register COUNT i;

    for(i = 0; *str; i++, str++)
        if(*str == chr)    return(i);
    return(-1);
}

/*
** Convert a hex digit (ASCII)
*/
INTEGER hex(c)
register CHARACTER c;
{
        if (isdigit(c))
                return (c - '0');
        else if ('a' <= c && c <= 'f')
                return (c + 10 - 'a');
        else if ('A' <= c && c <= 'F')
                return (c + 10 - 'A');
        else
                return(0);
}
         if (i == T_EOL && !is_eof
                                        && *linep == 0) {