没有使用cmath.h，提示cmath.h一大堆错误

C/C++ code

#include<stdio.h>#include<string>#define LEN 25#define SIZE 5void showinfo(struct person info[],int size);struct names {    char firstname[LEN];    char middlename[LEN];    char lastname[LEN];};struct person {    int ssn;    struct names name;};int main(void){    int i;    struct person people[SIZE];        for(i=0;i<SIZE;i++)    {        printf("Enter first name:");        gets(people[i].name.firstname);        printf("Enter middle name:");        gets(people[i].name.middlename);        printf("Enter last name:");        gets(people[i].name.lastname)==NULL;        printf("Enter SSN:");        scanf("%d",people[i].ssn);        while(getchar()!='\n');    }    showinfo(people,SIZE);    return 0;}void showinfo(person info[],int size){    int i;    for(i=0;i<size;i++)    {        printf("%s, %s",info[i].name.lastname,info[i].name.firstname);        if(info[i].name.middlename[0]!='\0')            printf(" %c.",info[i].name.middlename[0]);        printf(" - %d\n",info[i].ssn);    }}