IEEE float和int相互轉換

#include <iostream>
#include <regex>
#include <stdint.h>
#include <stdio.h>
#include <sstream>
using namespace std;

bool valid(string str){
    const regex pattern("[0-9a-fA-F]{2} [0-9a-fA-F]{2} [0-9a-fA-F]{2} [0-9a-fA-F]{2}");
    return regex_match(str,pattern);

}
bool parse(string str,float &f){
    uint32_t num;

    for(string::iterator itr=str.begin();itr!=str.end();itr++)
    {
        if(*itr==' '){
            str.erase(itr);
        }
    }
    str="0x"+str;
    sscanf(str.c_str(),"%x",&num);
    f=*((float*)&num);
    cout<<f<<endl;
}
std::string ieee_float_to_hex( float f )
{
    static_assert( std::numeric_limits<float>::is_iec559,
                   "必須輸入符合的浮點數" ) ;

    union { float fval ; std::uint32_t ival ; };
    fval = f ;

    std::ostringstream stm ;
    stm << std::hex << std::uppercase << ival<<endl;

    return stm.str() ;
}
void display(){
    std::cout<<"*            1.選0，float------>int;           *"<<endl;
    std::cout<<"*            1.選1，int------>float;           *"<<endl;
    std::cout<<"*            1.選2，直接退出                   *"<<endl;
    std::cout<<"*                                              *"<<endl;
    std::cout<<"************************************************"<<endl;
    std::cout<<"請選擇：";
}

int main(int argc, char const* argv[])
{
    string str;
    int select;
    float f;
    unsigned char byte[4];
    while(true)
    {
        display();
        cin>>select;
        switch(select)
        {
            case 0:
                std::cout<<"請輸入數字 (int 四位輸入時隔空格，由低位字節向高位字節排序"<<endl;
                std::cout<<"數字:";
                getchar();
                getline(cin,str);
                parse(str,f);
                break;
            case 1:
                cout<<"請輸入一個浮點數";
                std::cout<<"輸入：";
                cin>>f;
                cout<<ieee_float_to_hex(f);
            case 2:
                return 0;
        }
    }
        return 0;
}