bool search_value_loop(std::vector <int> &ivec,const int search_value,std::vector <int> ::difference_type & position){

 auto start=ivec.cbegin();

 auto end=ivec.cend();

 auto mid=start+(end-start)/2;

// std::cout<<*mid<

 while(mid!=end && *mid!=search_value){

 if(*mid
 start=mid+1;
 }else{
 end=mid-1;
 }
 mid=start +(end-start)/2;
 }
 if(*mid==search_value){
 position=mid-ivec.cbegin()+1;
 return true;
 }
 return false;


}


int main()
{
 bool rest;
 vector <int> ::difference_type position;
 vector <int> ivec={1,2,3,4,18,23,85,122};
 rest=search_value_loop(ivec,122,position);
 if(!rest){
 std::cout<<"no match values"<<std::endl;
 }else{
 std::cout<std::endl;
 }
}