书上例子-简单的atof函数

#include <ctype.h>
/*简单的字符串转浮点型函数*/
double atof(char s[]);

int main()
{
	return 0;
}

double atof(char s[])
{
	double val, power;
	int i, sign;
	for(i = 0; isspace(s[i]); i++)
		;
	sign = s[i] == '-'? -1: 1;

	if(s[i] == '-' ||　s[i] == '+')
		i++;
	for(val = 0.0; isdigit(s[i]); i++)
		val = 10.0 * val + (s[i] - '0');
	if(s[i] == '.')
		i++;
	for(power = 1.0; isdigit(s[i]); i++)
	{
		val = 10.0 * val + (s[i] - '0');
		power *= 10;
	}
	return sign * val / power;

}