如何在 C++ 中将浮点数转换为无符号整数？

Question

I want to convert a float to an unsigned int. When I use this code, the terminal print 3:

#include <iostream>

int main() {
  float test = 3.4;
  std::cout << "test : " << int(test) << "\n";
}

But when I use this code I have an error:

#include <iostream>

int main() {
  float test = 3.4;
  std::cout << "test : " << unsigned int(test) << "\n";
}

My error is:

example.cc: In function ‘int main()’:
example.cc:5:29: error: expected primary-expression before ‘unsigned’
    5 |   std::cout << "test : " << unsigned int(test) << "\n";
      |    

Can someone help me? I need to use an unsigned int. Thanks !

Answer 1

The functional cast ( type(expr) , that is) requires the type to be spelled as a single word (without spaces, [] , * , & , etc).

unsigned int is not a single word, so it's not allowed.

Your options are:

• Using the regular C-style cast: (unsigned int)test .

• Omitting the int . unsigned alone means the same thing as unsigned int , so you can write unsigned(test) .

• Using a static_cast : static_cast<unsigned int>(test) .