/* Yacc productions for "expr" command: */ %token OR AND ADD SUBT MULT DIV REM EQ GT GEQ LT LEQ NEQ%token A_STRING SUBSTR LENGTH INDEX NOARG MATCH /* operators listed below in increasing precedence: */%left OR%left AND%left EQ LT GT GEQ LEQ NEQ%left ADD SUBT%left MULT DIV REM%left MCH%left MATCH%left SUBSTR%left LENGTH INDEX %{#define YYSTYPE charp typedef char *charp;%} %% /* a single `expression' is evaluated and printed: */ expression:	expr NOARG = {			prt(1, $1);			exit((!strcmp($1,"0")||!strcmp($1,"\0"))? 1: 0);			}	;  expr:	'(' expr ')' = { $$ = $2; }	| expr OR expr   = { $$ = conj(OR, $1, $3); }	| expr AND expr   = { $$ = conj(AND, $1, $3); }	| expr EQ expr   = { $$ = rel(EQ, $1, $3); }	| expr GT expr   = { $$ = rel(GT, $1, $3); }	| expr GEQ expr   = { $$ = rel(GEQ, $1, $3); }	| expr LT expr   = { $$ = rel(LT, $1, $3); }	| expr LEQ expr   = { $$ = rel(LEQ, $1, $3); }	| expr NEQ expr   = { $$ = rel(NEQ, $1, $3); }	| expr ADD expr   = { $$ = arith(ADD, $1, $3); }	| expr SUBT expr   = { $$ = arith(SUBT, $1, $3); }	| expr MULT expr   = { $$ = arith(MULT, $1, $3); }	| expr DIV expr   = { $$ = arith(DIV, $1, $3); }	| expr REM expr   = { $$ = arith(REM, $1, $3); }	| expr MCH expr	 = { $$ = match($1, $3); }	| MATCH expr expr = { $$ = match($2, $3); }	| SUBSTR expr expr expr = { $$ = substr($2, $3, $4); }	| LENGTH expr       = { $$ = length($2); }	| INDEX expr expr = { $$ = index($2, $3); }	| A_STRING	;%%/*	expression command */#include <stdio.h>/* get rid of yacc debug printf's */#define printf#define ESIZE	512#define error(c)	errxx(c)#define EQL(x,y) !strcmp(x,y)long atol();char *ltoa();char	**Av;int	Ac;int	Argi; char Mstring[1][128];char *malloc();extern int nbra;int yyparse(void); voidmain(int argc, char **argv){	Ac = argc;	Argi = 1;	Av = argv;	yyparse();} char *operator[] = { "|", "&", "+", "-", "*", "/", "%", ":",	"=", "==", "<", "<=", ">", ">=", "!=",	"match", "substr", "length", "index", "\0" };int op[] = { OR, AND, ADD,  SUBT, MULT, DIV, REM, MCH,	EQ, EQ, LT, LEQ, GT, GEQ, NEQ,	MATCH, SUBSTR, LENGTH, INDEX };yylex() {	register char *p;	register i; 	if(Argi >= Ac) return NOARG; 	p = Av[Argi++]; 	if(*p == '(' || *p == ')')		return (int)*p;	for(i = 0; *operator[i]; ++i)		if(EQL(operator[i], p))			return op[i]; 	yylval = p;	return A_STRING;} char*rel(int op, char *r1, char *r2){	register i; 	if(ematch(r1, "-\\{0,1\\}[0-9]*$") && ematch(r2, "-\\{0,1\\}[0-9]*$"))		i = atol(r1) - atol(r2);	else		i = strcmp(r1, r2);	switch(op) {	case EQ: i = i==0; break;	case GT: i = i>0; break;	case GEQ: i = i>=0; break;	case LT: i = i<0; break;	case LEQ: i = i<=0; break;	case NEQ: i = i!=0; break;	}	return i? "1": "0";} char*arith(int op, char *r1, char *r2){	long i1, i2;	register char *rv; 	if(!(ematch(r1, "-\\{0,1\\}[0-9]*$") && ematch(r2, "-\\{0,1\\}[0-9]*$")))		yyerror("non-numeric argument");	i1 = atol(r1);	i2 = atol(r2); 	switch(op) {	case ADD: i1 = i1 + i2; break;	case SUBT: i1 = i1 - i2; break;	case MULT: i1 = i1 * i2; break;	case DIV: i1 = i1 / i2; break;	case REM: i1 = i1 % i2; break;	}	rv = malloc(16);	strcpy(rv, ltoa(i1));	return rv;}char*conj(int op, char *r1, char *r2){	register char *rv; 	switch(op) { 	case OR:		if(EQL(r1, "0")		|| EQL(r1, ""))			if(EQL(r2, "0")			|| EQL(r2, ""))				rv = "0";			else				rv = r2;		else			rv = r1;		break;	case AND:		if(EQL(r1, "0")		|| EQL(r1, ""))			rv = "0";		else if(EQL(r2, "0")		|| EQL(r2, ""))			rv = "0";		else			rv = r1;		break;	}	return rv;} char*substr(char *v, char *s, char *w){register si, wi;register char *res; 	si = atol(s);	wi = atol(w);	while(--si) if(*v) ++v; 	res = v; 	while(wi--) if(*v) ++v; 	*v = '\0';	return res;} char*length(char *s){	register i = 0;	register char *rv; 	while(*s++) ++i; 	rv = malloc(8);	strcpy(rv, ltoa((long)i));	return rv;} char*index(char *s, char *t){	register i, j;	register char *rv; 	for(i = 0; s[i] ; ++i)		for(j = 0; t[j] ; ++j)			if(s[i]==t[j]) {				strcpy(rv=malloc(8), ltoa((long)++i));				return rv;			}	return "0";} char*match(char *s, char *p){	register char *rv; 	strcpy(rv=malloc(8), ltoa((long)ematch(s, p)));	if(nbra) {		rv = malloc(strlen(Mstring[0])+1);		strcpy(rv, Mstring[0]);	}	return rv;} #define INIT	register char *sp = instring;#define GETC()		(*sp++)#define PEEKC()		(*sp)#define UNGETC(c)	(--sp)#define RETURN(c)	return#define ERROR(c)	errxx(c) intematch(char *s, char *p){	static char expbuf[ESIZE];	char *compile();	register num;	extern char *braslist[], *braelist[], *loc2; 	compile(p, expbuf, &expbuf[ESIZE], 0);	if(nbra > 1)		yyerror("Too many '\\('s");	if(advance(s, expbuf)) {		if(nbra == 1) {			p = braslist[0];			num = braelist[0] - p;			strncpy(Mstring[0], p, num);			Mstring[0][num] = '\0';		}		return(loc2-s);	}	return(0);} errxx(int c){	yyerror("RE error");} #include  "regexp.h"yyerror(char *s){	write(2, "expr: ", 6);	prt(2, s);	exit(2);}prt(int fd, char *s){	write(fd, s, strlen(s));	write(fd, "\n", 1);}char*ltoa(long l){	static char str[20];	register char *sp = &str[18];	register i;	register neg = 0; 	if(l < 0)		++neg, l *= -1;	str[19] = '\0';	do {		i = l % 10;		*sp-- = '0' + i;		l /= 10;	} while(l);	if(neg)		*sp-- = '-';	return ++sp;}