casting - C++ static_cast< int > (str.size()-1) means? -

i getting stuck when using line , not able understand.

can tell me mean of

while(i < static_cast<int>(str.size() - 1)) 

in following code?

#include <iostream>  using namespace std;  int main() {     string str;     cin >> str;     int = 0;      while(i < static_cast<int>(str.size() - 1)) {         if(i > -1 && str[i] == str[i + 1]) {             str.erase(i,2);             i--;         }          else {             i++;         }     }      if(str.empty())        cout << "empty string" << endl;     else        cout << str << endl;      return 0; } 

if compare signed , unsigned integer, compiler warn that. e.g. gcc show following warning message:

warning: comparison between signed , unsigned integer expressions [-wsign-compare]

the std::string::size returns unsigned integer, std::size_t implementation-defined type , can store maximum size of theoretically possible object of type.

if want suppress these warnings, have cast signed integer unsigned before comparison. code snippet questioning opposite: casts (with static_cast) std::size_t (unsigned) type int (signed) type. this bad practice because if str.size() - 1 higher int_max, produce implementation-defined behaviour.