为函数原型写函数定义：double my_atof(char *str)；

#include<stdio.h>  double my_atof(char *str){int i=0,a=1,j=0;double s=0;while(str[i]!='\0'){j*=10;if(str[i]=='-'){a=-1;;}if(str[i]=='.'){j=1;}if((str[i]>='0')&&(str[i]<='9')){s=10*s+(str[i]-'0');}if(str[i]==' '){j=j/10;}i++;}return ((s*a)/j);}int main(){char t[10]={'-','1',' ','2','.','3','4',' ','9'};printf("%lf\n",my_atof(t));return 0;}