# include & lt; List> 
# include & lt; Thread> 

using namespace std; 
Struct Data 
{
Int the from; 
int to; 
Long long sum; 
}; 
Data sum (int the from, int to) 
{
The Data s; 
While (true) 
{
S. ROM=the from; 
S.t o=to; 
S.s um=0; 
For (int I=the from; i <=to; I++) 
{
S.s um +=I; 
} 
For (int I=to; I & gt;=(to a + from)/2; I -) 
{
S.s um -=I; 
} 
} 

//printf (" % d +... + % d % d... - % d=% LLD \ n ", s. ROM, s.t o, s.t o, (s.t o + from)/2, s.s um); 
//this_thread: : sleep_for (STD: : chrono: : milliseconds (50)); 
return s; 
} 


Int main (int arg c, char * argv []) 
{
QCoreApplication a (arg c, argv); 

STD: : future RetData=https://bbs.csdn.net/topics/std::async (STD: : bind (& sum, 20, 100000)); 
while(! RetData. Valid ()) 
{
continue; 
} 
Cout<" Data Reday "& lt; Data r=retData. The get (); 
Cout<" From: "& lt; return 0; 
} 

Himself in the use of the future, I found there is something wrong with the valid value of the future, when I have an infinite loop, this code results check value valid returns true, cause in the console to play out, and then get places, etc., this is obviously wrong,
When I was in the use of thread pool found this problem, when I was in the main thread to check the future, I think that value is ready, result in equivalent, didn't do other things to do, please explain a great god, the wrong place and correct use thank you
I use the IDE: 5.9.3 + vc2015 x86