nepc.l.c

一个小计算器的实现(编译原理),用Lex和bison

%{

#include "nepc.tab.h"
#include "nepc.h"
 static int input();
%}

digit       [0-9]
xdigit      [0-9a-fA-F]
odigit      [0-7]

dec_int     0|[1-9]{digit}*
dec_flt   (0\.{digit}*)|([1-9]{digit}*\.{digit}*)
oct_int     0{odigit}+
hex_int     0(x|X){xdigit}+
   
other      [-()<>=+*.;%]
letter      [a-zA-Z]

variable    {letter}({letter}|{digit})*
 
 
%x          ASTRING
%%
                char *s, *v;
                char tmpstr[MAX_STRLEN];
\"              { BEGIN ASTRING; s = tmpstr; }

<ASTRING>\\t    { *s++ = '\t'; /* CARE BUFFER OVERFLOW HERE!!! */ }
<ASTRING>\\\"   { *s++ = '\"'; /* CARE BUFFER OVERFLOW HERE!!! */ }
<ASTRING>\"     {
                    *s = '\0';
                    BEGIN 0; 
                    yylval.pStr = tmpstr;
                    return STRING;
                }

<ASTRING>.      { *s++ = *yytext; }

"int"       return TYPE_INT;
"float"       return TYPE_FLOAT;
"double"       return TYPE_DOUBLE;
"long"       return TYPE_LONG;
"string"       return TYPE_STRING;
"struct"       return TYPE_STRUCT;



"while"     return WHILE;
"for"     return FOR;
"if"        return IF;
"else"      return ELSE;
"print"     return PRINT;

"exit"      return EXIT;
"quit"      return EXIT;
"erase"     return ERASE;
"clear"     return CLEAR;
"cls"       return CLEAR;
"ls"        return LIST;
"list"      return LIST;
"help"      return HELP;
"dec"       return DEC;
"hex"       return HEX;
"oct"       return OCT;

"acos"      return ACOS;
"asin"      return ASIN;
"atan"      return ATAN;
"ceil"      return CEIL;
"cos"       return COS;
"cosh"      return COSH;
"exp"       return EXP;
"fabs"      return FABS;
"floor"     return FLOOR;
"log"       return LOG;
"log10"     return LOG10;
"sin"       return SIN;
"sinh"      return SINH;
"sqrt"      return SQRT;
"tan"       return TAN;
"tanh"      return TANH;
"/*"        { comment(); }

"//"        { comment2(); }
{variable}  {
                v=malloc(yyleng+1);
                strncpy(v, yytext, yyleng);
                v[yyleng]='\0';
                yylval.pStr = v;
                return VARIABLE;
            }

{dec_int}   {
                yylval.iValue = STR_TO_INT(yytext);
                return INTEGER;
            }

{dec_flt}   {
                yylval.fValue = STR_TO_FLT(yytext);
                return FLOAT;
            }

{oct_int}   {
                int i=1; 
                INT val=0;
                while(i<yyleng)
                {
                    val=(val<<3)+yytext[i]-'0';
                    i++;
                }
                yylval.iValue=val;
                return INTEGER;
            }





{hex_int}   {
                int i=2;
                INT val=0;
                while(i<yyleng)
                {
                    if(islower(yytext[i])) val=(val<<4)+yytext[i]-'a'+10;
                    else if(isupper(yytext[i])) val=(val<<4)+yytext[i]-'A'+10;
                    else val=(val<<4)+yytext[i]-'0';
                    i++;
                }
                yylval.iValue=val;
                return INTEGER;
            }

[-()<>=+*/{}.;%] {
                    return *yytext;
                }
">="            return GE;
"<="            return LE;
"=="            return EQ;
"!="            return NE;
"&&"            return AND;
"||"            return OR;
"++"            return PP;
"--"            return SS;

[ \t]+        { }  ;       /* ignore whitespace */
"\n"  {G_line++; }
.               yyerror("Unknown character");


%%
int yywrap(void) 
{
    return 1;
}

comment()
{
	char c, c1;

loop:
	while ((c = input()) != '*' && c != 0)
	{

		putchar(c);
		if(c=='\n')
		{
			G_line++;
		}
	}

	if ((c1 = input()) != '/' && c != 0)
	{
		if(c1=='\n')
		{
			G_line++;
		}
		unput(c1);
		goto loop;
	}

	if (c != 0)
	{
		putchar(c1);
		if(c1=='\n')
		{
			G_line++;
		}
	}

}

comment2()  
{   
	char c, c1;
 
loop:
	while ((c = input()) != '\n' && c != 0)
	{

		putchar(c);

	}
 
}