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#include <stdio.h>
#include <ctype.h>
/* The C Programming Language: 2nd Edition
*
* Exercise 5-1: As written, getint treats a + or - not followed by a digit as
* a valid representation of zero. Fix it to push such a character back on the
* input.
*/
#define BUFSIZE 100
int getch(void);
void ungetch(int);
int getint(int *);
char buf[BUFSIZE];
int bufp = 0;
int main() {
int foo;
int *bar = &foo;
while (getint(bar) > 0) {
printf("%d\n", foo);
}
printf("Contents of buffer:%s\n", buf);
return 0;
}
int getint(int *pn) {
int c, sign;
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(c);
ungetch(sign == 1 ? '+' : '-');
return 0;
}
}
if (!isdigit(c)) {
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;
}
int getch(void) {
return (bufp > 0) ? buf[--bufp] : getchar();
}
void ungetch(int c) {
if (bufp >= BUFSIZE) {
printf("ungetch: Too many characters.\n");
} else {
buf[bufp++] = c;
}
}
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