Exercise 5.02

Page 97

Write getfloat, the floating-point analog of getint. What type does getfloat return as its function value?

#include <stdio.h>
#include <ctype.h>

#define SIZE 100

int main()
{
	int i, isfloat, getfloat(float *);
	float array[SIZE];

	for (i = 0; i < SIZE && (isfloat = getfloat(&array[i])) != EOF;
	     isfloat ? i++ : (void)0)
		;

	for (int j = 0; j < i; j++) {
		printf("%g\n", array[j]);
	}
}

int getch(void);
void ungetch(int);

int getfloat(float *pf)
{
	int c, sign, power;

	while (isspace(c = getch()))
		;

	if (!isdigit(c) && c != '+' && c != '-' && c != '.' && c != EOF) {
		return 0;
	}

	sign = (c == '-') ? -1 : 1;

	if (c == '+' || c == '-') {
		c = getch();
		if ((c <= '0' || c >= '9') && c != '.') {
			return 0;
		}
	}

	power = 0;
	for (*pf = 0; isdigit(c) || c == '.'; c = getch()) {
		power *= 10;
		if (c == '.') {
			power = 1;
		} else {
			*pf = 10 * *pf + (c - '0');
		}
	}
	if (power > 0) {
		*pf /= power;
	}
	*pf *= sign;

	if (c != EOF) {
		ungetch(c);
	}

	return c;
}

#define BUFSIZE 100
char buf[BUFSIZE];
int bufp = 0;

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;
	}
}