c++ - Why is an explicit comparison needed when using try_lock()? -

i reading documentation of std::mutex::try_lock , had example on it:

#include <iostream> #include <mutex>  int main() {     std::mutex test;     if (test.try_lock() == true)         std::cout << "lock acquired" << std::endl;     else         std::cout << "lock not acquired" << std::endl;     test.unlock();  // unlock mutex     test.lock();    // lock again     if (test.try_lock())  // true can left out         std::cout << "lock acquired" << std::endl;     else         std::cout << "lock not acquired" << std::endl;     test.lock(); // , finale (a block) } 

in second if statement says true can left out. why second 1 not first. checked , says try_lock returns boolean, how can not either true or false, making == true check superfluous?

x == true silly when x has type bool. test.try_lock() returns bool, in both cases test isn't needed.