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#include <stdio.h>
#include <math.h>
/* The C Programming Language: 2nd Edition
*
* Exercise 5-2: Write getfloat, the floating-point analog of getint. What
* type does getfloat return as its function value?
*
* Answer: getfloat should return an integer, since getint's return value is
* only important to check its status, not the value type that it's working
* with. The only real "gotcha" here is making sure to use getch() after
* checking for a decimal point so the resulting loop will actually execute.
*/
#define BUFSIZE 100
int getch(void);
void ungetch(int);
int getfloat(double *);
char buf[BUFSIZE];
int bufp = 0;
int main() {
double foo;
double *bar = &foo;
while (getfloat(bar) > 0) {
printf("%f\n", foo);
}
return 0;
}
int getfloat(double *pn) {
int c, sign, places;
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 (c != '.' && !isdigit(c)) {
return 0;
}
for (*pn = 0.0; isdigit(c); c = getch()) {
*pn = 10.0 * *pn + (c - '0');
}
if (c == '.') {
c = getch(); // skip the decimal point or the loop won't trigger
for (places = -1; isdigit(c); c = getch()) {
*pn += (double)(c - '0') * pow(10, places--);
}
}
*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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