自学教程：C++ ungetch函数代码示例

/** get next token/lexem */int gettoken(void) {	int c, getch(void);	void ungetch(int);	char *p = token;	/** skip whitespaces */	while ((c = getch()) == ' ' || c == '/t')		;	/** collect '(' and "()" tokens */	if (c == '(') {		if ((c = getch()) == ')') {			strcpy(token, "()");			return tokentype = PARENS;		}		else {			ungetch(c);			return tokentype = '(';		}	}	/** collect "[SIZE]" tokens */	else if (c == '[') {		for (*p++ = c; (*p++ = getch()) != ']'; )			;		*p = '/0';		return tokentype = BRACKETS;	}	/** collect "NAME" tokens */	else if (isalpha(c)) {		for (*p++ = c; isalnum(c = getch()); )			*p++ = c;		*p = '/0';		ungetch(c);		return tokentype = NAME;	}	/** collect everything else */	else		return tokentype = c;}

int get_token(void){  int c, getch(void);  void ungetch(int);  char *p = token;  while ((c = getch()) == ' ' || c == '/t')      ;  if (c == '(')  {    if ((c = getch()) == ')')    {      strcpy(token, "()");      return tokentype = PARENS;    }    else    {      ungetch(c);      return tokentype = '(';    }  }  else if (c == '[')  {    for (*p++ = c; (*p++ = getch()) != ']'; )      ;    *p = '/0';    return tokentype = BRACKETS;  }  else if (isalpha(c))  {    for (*p++ = c; isalnum(c = getch()); )      *p++ = c;    *p = '/0';    ungetch(c);    return tokentype = NAME;  }  else    return tokentype = c;}

int main(int argc, char *argv[]) {	char word[MAXWORD];	char word2[MAXWORD];	int i;	struct nlist *np;		struct tnode *root;	root = NULL;	while (getword(word, MAXWORD) != EOF) {		if (strcmp(word, "#define") == 0 && getword(word, MAXWORD) != EOF &&			isalpha(word[0]) && getword(word2, MAXWORD) != EOF) {			install(word, word2);		} else if (isalpha(word[0])) {			if ((np = lookup(word)) != NULL) {				i = strlen(np->defn) - 1;				while (i >= 0) {					ungetch(np->defn[i]);					i--;				}			} else {				root = addtree(root, word);			}		}	}	/*	INPUT:	#define a x	#define x e	a	x	x	c	v	b	a	q	e		OUTPUT:	1 b	1 c	5 e	1 q	1 v	*/	treeprint(root);	return 0;}

bool QFile::open( int m, FILE *f ){    if ( isOpen() ) {#if defined(QT_CHECK_RANGE)	qWarning( "QFile::open: File already open" );#endif	return FALSE;    }    init();    setMode( m &~IO_Raw );    setState( IO_Open );    fh = f;    ext_f = TRUE;    struct stat st;    ::fstat( fileno(fh), &st );#if defined(QT_LARGEFILE_SUPPORT)#if !defined(QT_ABI_QT4)    off_t tmp = ftello( fh );    ioIndex = tmp > UINT_MAX ? UINT_MAX : (Offset)tmp;#else    ioIndex = (Offset)ftello( fh );#endif#else    ioIndex = (Offset)ftell( fh );#endif    if ( (st.st_mode & S_IFMT) != S_IFREG || f == stdin ) { //stdin is non seekable	// non-seekable	setType( IO_Sequential );	length = INT_MAX;	ioIndex = 0;    } else {#if defined(QT_LARGEFILE_SUPPORT) && !defined(QT_ABI_QT4)	length = st.st_size > UINT_MAX ? UINT_MAX : (Offset)st.st_size;#else	length = (Offset)st.st_size;#endif	if ( !(flags()&IO_Truncate) && length == 0 && isReadable() ) {	    // try if you can read from it (if you can, it's a sequential	    // device; e.g. a file in the /proc filesystem)	    int c = getch();	    if ( c != -1 ) {		ungetch(c);		setType( IO_Sequential );		length = INT_MAX;		ioIndex = 0;	    }	    resetStatus();	}    }    return TRUE;}

int getint(int *pn){        /* Get next integer from input into *pn. */        int c;        int sign;        while (isspace(c = getch()))                continue;        if (!isdigit(c) && c != EOF && c != '+' && c != '-') {                printf("%c is not a number or sign/n", c);                ungetch(c);                return 0;        }        sign = (c == '-') ? -1 : 1;        if (c == '+' || c == '-') {                c = getch();                if (!isdigit(c)) {                        /* push both characters back on input */                        ungetch((sign == 1) ? '+' : '-');                        ungetch(c);                        return 0;                }        }        for (*pn = 0; isdigit(c); c = getch())                *pn = 10 * *pn + (c - '0');        *pn *= sign;        if (c != EOF)                ungetch(c);        return c;}

/*gettop: get next character or operand */int getop(char s[]){	int i, c;	double r;	while ( (s[0] = c = getch() ) == ' ' || c == '/t')					;	s[1] = '/0';		i = 0;	if (!isdigit(c) && c != '.' && c != '-')    		return c; /* not a number */	if (c == '-')                                        /* section to check negative values */		if (isdigit(c = getch()) || c == '.')        /* if a negative symbol detects */			s[++i] = c; /* negative number*/     /* check whether next character is a number or a  '.' if so */		else { 					     /* that is negative number & that will be stored in the array to be returned*/			if (c != EOF)			     /* else return a negative operator to compute */ 				ungetch(c);			return '-';		} 		if (isdigit(c)) /* collect integer parts */		while (isdigit(s[++i] = c = getchar()))			;	if (c == '.')		while (isdigit(s[++i] = c = getchar()));			;	s[i] = '/0';	if (c != EOF)		ungetch(c);	return NUMBER;/*	if (c == '/n') {		i = 1;		r = val[--sp];		printf("/t%.8g", r);	} */}

/* getop: get next operator or numeric operand */int getop(char input[]) {  int i, c;  while ((input[0] = c = getch()) == ' ' || c == '/t') {    ;  }  input[1] = '/0';  if (!isdigit(c) && c != '.' && c != '-') {    return c;           /* not a number */  }  i = 0;  if (c == '-') {    if (isdigit(input[++i] = c = getch())) {      ;                 /* negative number */    } else {      ungetch(c);       /* not a negative, so backup and return negative */      return '-';    }  }  if (isdigit(c)) {     /* collect integer part */    while (isdigit(input[++i] = c = getch())) {      ;    }  }  if (c == '.') {       /* collect fraction part */    while (isdigit(input[++i] = c = getch())) {      ;    }  }  input[i] = '/0';  if (c != EOF) {    ungetch(c);  }  return NUMBER;}

/* getop: получает следующий оператор или операнд */int getop(char s[]){    int i = 0, c;    while ((c = getch()) == ' ' || c == '/t' )        ;    s[1] = '/0';    if (!isdigit(c) && c != '.') {        if (c == '-') {            s[i++] = c;            if (!isdigit(c = getch())) {                ungetch(c);                return s[--i]; /* не число */            }        } else {            return c; /* не число */        }    }    /* накапливаем целую часть */    if (isdigit(c)) {        s[i++] = c;        while (isdigit(s[i++] = c = getch()))            ;    }    /* накапливаем дробную часть */    if (c == '.') {        s[i++] = c;        while (isdigit(s[i++] = c = getch()))            ;    }    if (!isdigit(s[i - 1]))        --i;    if (c != EOF)        ungetch(c);    s[i] = '/0';    return NUMBER;}

// Возвращает строку s во входной потокvoid ungets(char s[]) {    // Узнаём размер    int pos;    for (pos = 0; s[pos] != '/0' && s[pos] != '/n' && s[pos] != EOF; pos++)        ;    --pos;    // Возвращаем с конца в буфер    while (pos >= 0) {        ungetch(s[pos]);        --pos;    }}

/* ungets: push back an entire string onto the input */void ungets(char s[]){	char c;	int i;	/* read input line and push back all its characters */	for (i = 0; (c = getchar()) != NEWLINE; i++)		ungetch(c);	s[i++] = NEWLINE;	s[i] = NULLCHAR;	/* get pushed back characters, newline and nullchar remain in place */	for (i = i - 2; i >= 0; i--)		s[i] = getch();}

int kbhit(void) {    int temp;    if (!screen_initialized) init_screen();    wtimeout(stdscr, 0);    if ((temp = wgetch(stdscr)) != EOF) {        ungetch(temp);        nodelay(stdscr, FALSE);        return TRUE;    } else {        nodelay(stdscr, FALSE);        return FALSE;    }}

char *cgets(char *string){    unsigned len = 0;    unsigned int maxlen_wanted;    char *sp;    int c;    /*     * Be smart and check for NULL pointer.     * Don't know wether TURBOC does this.     */    if (!string)	return (NULL);    maxlen_wanted = (unsigned int) ((unsigned char) string[0]);    sp = &(string[2]);    /*     * Should the string be shorter maxlen_wanted including or excluding     * the trailing '/0' ? We don't take any risk.     */    while (len < maxlen_wanted - 1) {	c = getch();	/*	 * shold we check for backspace here?	 * TURBOC does (just checked) but doesn't in cscanf (thats harder	 * or even impossible). We do the same.	 */	if (c == '/b') {	    if (len > 0) {		cputs("/b /b");	/* go back, clear char on screen with space				   and go back again */		len--;		sp[len] = '/0';	/* clear the character in the string */	    }	} else if (c == '/r') {	    sp[len] = '/0';	    break;	} else if (c == 0) {	    /* special character ends input */	    sp[len] = '/0';	    ungetch(c);		/* keep the char for later processing */	    break;	} else {	    sp[len] = putch(c);	    len++;	}    }    sp[maxlen_wanted - 1] = '/0';    string[1] = (char) ((unsigned char) len);    return (sp);}

int getword(char *word, int lim){	int c, getch(void);	void ungetch(int);	char *w = word;	while (isspace(c = getch())){		/*if (c=='/n'){			return 0*/;	//	}	;}	if(c==EOF)		return EOF;		if (isalpha(c)){		*w++ = c;	}	if (!isalpha(c)) {		if(c=='/'){			if((c=getch())=='*'){					while((c=getch())!='*')						;					if((c=getch())=='/'){						if((c=getch())=='/n'){							return 1;}					}			}		}			if(c=='"'){			while((c=getch())!='"')				;		if((c=getch())=='/n')			return 1;		}	}	for ( ; --lim > 0; w++)		if (!isalnum(*w = getch())&&*w!='_'&&*w!='.') 		{			if(*w=='/n'){				*w='/0';				return 1;			}			ungetch(*w);			break;		}		*w = '/0';		return 1;}

int comment(void){    int getch(void);    void ungetch(int);    int c;    while((c = getch()) != EOF)        if(c == '*'){            if((c = getch()) == '/')                break;            else                ungetch(c);        }    return c;}

int main(void) {    int c;    while ((c = getch()) != EOF) {        if (c == '/n'); // Do nothing        else if (c >= '0' && c <= '9') {            ungetch(c);            printf("[%c] is a number/n", getch());        } else            printf("[%c] is not a number/n", c);    }    return 0;}

double getdouble(double *pn) {    int i = 0, e = 0;    double b, c, sign;    while ((c = getch()) == ' ' || c == '/t')        ;    if (!isdigit(c) && c != EOF && c != '+' && c != '-' && c != '/n' && c != '.')        c = getdouble(&array[++n]);    sign = (c == '-') ? -1 : 1;    if (c == '+' || c == '-') {        if (isdigit(b = getch()))            c = b;        else            c = getdouble(&array[++n]);    }    if (c == '/n') {        printf("/n");        c = getdouble(&array[++n]);    }    if (c != EOF) {        *pn = 0;        i = 10 * i + (c - '0');        while (isdigit(c = getch()))            i = 10 * i + (c - '0');        if (c == '.') {            while(isdigit(c = getch())) {                *pn = 10.0 * *pn + (c - '0');                e--;            }        }        while (e < 0) {            *pn *= 0.1;            e++;        }        *pn += i;        *pn *= sign;        ungetch(c);    }    return c;}

intPOL::gettok (TOKEN *tok){  int c, toktype;  int inum;  double fnum;  int toksiz = MAXTOK;          /* maximum length of token string */  while ((c = inchar()) == BLANK || c == TAB)    ;  ungetch (c);  c = lookchar();  toktype = type(c);  fnum = 0.0;  inum = 0;  if (c == BLANK || c == TAB) {                 /* skip white space */    getblank(tok->tokstr, toksiz);    toktype = TT_BLANK;  } else if (toktype == LETTER) {    toktype = getalpha (tok->tokstr, toksiz);  } else if (c == meta.str) {                   /* quoted string */    getquote (tok->tokstr, toksiz);    toktype = TT_STRING;  } else if (type(c) == DIGIT || c == PLUS || c == HYPHEN || c == PERIOD) {    toktype = getnumber (tok->tokstr, toksiz, &fnum, &inum);  } else if (c == EOF) {    tok->tokstr[0] = EOS;    toktype = TT_EOF;  } else {    c = inchar();    tok->tokstr[0] = c;    tok->tokstr[1] = EOS;    toktype = TT_SPECLCHAR;  }  tok->type = toktype;  tok->ready = true;  if (tok->type == TT_REAL || tok->type == TT_INT) {    tok->fnum = fnum;    tok->inum = inum;  } else {    tok->fnum = 0.0;    tok->inum = 0;  }  return (toktype);}

int getfloat(float *pn){    int c, sign;    float power;        while(isspace(c=getch() ))          ;    if( !isdigit(c) && c !=EOF && c !='+' && c!= '-' && c != '.') {        ungetch(c);        return 0;    }        sign = (c== '-')? -1:1;        if (c== '+' || c == '-')       if(!isdigit(c =getch() && c != '.'){                     ungetch(c);                     return 0;       }    for(*pn =0; isdigit(c); c=getch())            *pn = 10.0* *pn + (c - '0');        if(c == '.')         getch(c);        for(*pn=0, power =1.0; isdigit(c); c=getch()){               *pn = 10.0 * *pn + (c - '0');               power *= 10.0;    }        *pn *= (sign/power);        if( c != EOF)        ungetch(c);    return c;    }

int gettoken(void) /* return next token */{	int c,getch(void);	void ungetch(int);	char *p = token;	if(prevtoken==YES)	{		prevtoken = NO;		return tokentype;	}	while((c=getch())==' '||c=='/t'){		;	}	if(c=='('){		if((c=getch())==')'){			strcpy(token,"()");			return tokentype=PARENS;		}else{			ungetch(c);			return tokentype=')';		}	}else if(c=='['){	   for(*p++=c;(*p++=getch())!=']';)			;		*p='/0';		return tokentype = BRACKETS;	}else if(isalpha(c)){		for(*p++=c;isalnum(c=getch());){			*p++=c;		}		*p='/0';		ungetch(c);		return tokentype = NAME;	}else{		return tokentype=c;	}}

/* getop:  get next operator or numeric operand */int getop(char s[]){	int i, c;		while ((s[0] = c = getch()) == ' ' || c == '/t') {		;	}	s[1] = '/0';	if (!isdigit(c) && c != '.') {		if (c == COMMAND) {			/* a command, read the command till a non-printable character */			for (i = 0; (s[i] = c = getch()) != ' ' && c != '/n' && c != '/t' && c != EOF; ++i) {				;			}			ungetch(c); /* return the extra character read */			s[i] = '/0'; /* terminate the command string */			return COMMAND;		}		return c; /* not a number, not a comamnd, this is an operator */	}	i = 0;	if (isdigit(c)) { /* collect integer part */		while (isdigit(s[++i] = c = getch())) {			;		}	}	if (c == '.') { /* collect fraction part */		while (isdigit(s[++i] = c = getch())) {			;		}	}	s[i] = '/0';	if (c != EOF) {		ungetch(c);	}	return NUMBER;}

/* getop: get next operator or numeric operand*/int getop(char s[]){    int i, c;    int c2;    while ((c = getch()) == ' ' || c == '/t')	;    s[0] = c;    s[1] = '/0';    i = 1;    if (!isdigit(c) && c != '.') {	if (c == '-'){	    c2 = getch();	    if (isdigit(c2) || c2 == '.') {		s[i++] = c2;	    }	    else {		ungetch(c2);		return c;	    }	}	else	    return c;    }        while (isdigit(c = getch()))	s[i++] = c;    if (c == '.') {	s[i++] = c;	while (isdigit(c = getch()))	    s[i++] = c;    }    s[i] = '/0';//    if (c != EOF)    ungetch(c);    return NUMBER;}

int getword(char *word, int lim, int *lineNum){	int		c;	char 	*w = word;	while (isspace(c = getch())){		//出现换行符		if ('/n' == c){			(*lineNum)++;		}	}	if (c != EOF && '/' != c){		*w++ = c;	}	if (!isalpha(c) && '_' != c && '/' != c){		*w = '/0';		return c;	}	if ((isalpha(c) || '_' == c) && '/' != c){		for (; --lim > 0; w++){			if (!isalnum(*w = getch()) && '_' != *w){				ungetch(*w);				break;			}		}	}	else if ('/' == c){		if ('*' == (c = getch())){			comment();		}		else{			ungetch(c);		}	}	*w = '/0';	return word[0];}

char *getnextoken(void){	int c;	char *bp = tokbuf;	for (;;) {		if ((c = getch()) < 0) return 0;		if (c ==  ' ' || c == '/t') continue;		if (c == '/n') {			*bp++ = c;			*bp = 0;			return tokbuf;		}		/* start of something */		ungetch(c);		break;	}		for (;;) {		if ((c = getch()) < 0) {			ungetch(c);			if (bp > tokbuf) {				*bp = 0;				return tokbuf;			}			return 0;		} else if (c == ' ' || c == '/t' || c == '/n') {			ungetch(c);			*bp = 0;			return tokbuf;		}		*bp++ = c;	}	return 0;	/* not reached */}

int getint ( int *pn ) {    int c = 0;    int sign = 0;    while ( isspace ( c = getch () ) ) {    }    if ( ! isdigit ( c ) && c != EOF && c != '+' && c != '-' ) {//        ungetch ( c );        return 0;    };    sign = ( c == '-' ) ? ( -1 ) : 1;    if ( c == '+' || c == '-' ) {        c = getch ();        if ( ! isdigit ( c ) ) {            ungetch ( ( sign == 1 ) ? '+' : '-' );            return 0;        }    };        for ( *pn = 0; isdigit ( c ); c = getch () ) {        *pn = 10 * *pn + ( c - '0' ) ;    };            *pn *= sign;    if ( c != EOF ) {        ungetch ( c );     }    return c;}

/* getop: get next operator or numeric operand, return type */int getop(char s[]){	int i, c, type;	i = 0;	while ( (s[i] = c = getch()) == ' ' || c == '/t')		;		/* skip white space */	if (c == '-') {		/* '-' could be operator or negative indicator */		s[++i] = c = getch();		if (!isdigit(c)) {			ungetch(c);			s[i] = '/0';			return s[0];		}	}	if (isop(c) || c == '/n') {	        s[i] = '/0';		return c;	} else if (isdigit(c) || c == '.') { /* digit */		type = NUMBER;		if (isdigit(c))		/* collect integer part */			while (isdigit(s[++i] = c = getch()))				;		if (c == '.')		/* collect fraction part */			while (isdigit(s[++i] = c = getch()))				;	} else {		/* handles any other input */		while ( (s[++i] = c = getch()) != ' ' && c != '/t' && c != '/n')			;		type = optype(s, i-1);	}	s[i] = '/0';	if (c != EOF)		ungetch(c);	return type;}

int getint(int *pn) {	int c, sign = 1;	c = getch();	while(isspace(c)) {		c = getch();	}	if(c != '+' && c != '-' && !isdigit(c) && c != EOF) {		ungetch(c);		return 0;	}	if(c == '+' || c == '-') {		if(c == '-') {			sign = -1;		}		c = getch();		if(!isdigit(c)) {			ungetch(c);			ungetch(sign == 1 ? '+' : '-');			return 0;		}	}	*pn = 0;	while(isdigit(c)) {		*pn = *pn * 10 + c - '0';		c = getch();	}	*pn *= sign;	if(c != EOF) {		ungetch(c);	}	return c;}

int main(int argc, char *argv[]){        // awesome code goes here:	int c;	while ((c = getch()) != EOF) {	//	if (c >= '0' && c <= '9')			printf("%c", c);		if (c < '0' && c > '9')				ungetch(c);			//printf(	}        return 0;}

/* getfloat - get next floating point value from input into *f * *   handle strings of digits with decimal points for now: * *      12.3   -89.0   23435.34301 * */int getfloat(double *f){    double val, power;    int c, sign;    while (isspace(c = getch()))     /* skip white space */        ;    if (!isdigit(c) && c != EOF && c != '+' && c != '-' && c != '.')    {        ungetch(c);        return 0;    }    sign = (c == '-') ? -1 : 1;    if (c == '+' || c == '-')    {        c = getch();        if (!isdigit(c) && c != '.')        {            ungetch(c);            return 0;        }    }    for (val = 0.0; isdigit(c); c = getch())        val = 10.0 * val + (c - '0');    if (c == '.')        c = getch();    for (power = 1.0; isdigit(c); c = getch())    {        val = 10.0 * val + (c - '0');        power *= 10.0;    }    *f = sign * val / power;    if (c != EOF)        ungetch(c);    return(c);}

int isAssigner(char s []){	int nextChar;	if (s[0] == '-')	{		nextChar = getch();		if (nextChar != '>')		{			ungetch(nextChar);			return 0;		}		return 1;	}	return 0;}

// getword: get word inputint getword(char *w, int lim) {	int c;	char *word = w;	while (isspace(c=getch()));	if (!isalpha(c) && c != '_')		return c;	for (*w++=c; w-word<lim-1 && (isalnum(c=getch()) || c=='_'); *w++=c);	if (w-word < lim-1) {		ungetch(c);		c = word[0];	}	*w = '/0';	return c;}