C++17: std::reduce()

C++17 added std::reduce(), which applies applies a binary operation on a range of elements. The default binary operation is addition. Here is an example (simulated with C++14):

#include <iostream>
#include <vector>

namespace std17
{
  template<class InputIt>
  typename std::iterator_traits<InputIt>::value_type
  reduce(InputIt first, InputIt last)
  {
    std::iterator_traits<InputIt>::value_type sum =
                 std::iterator_traits<InputIt>::value_type();
    for (auto iter = first; iter != last; iter++)
    {
      sum = sum + *iter;
    }
    return sum;
  }
}

int main()
{
  std::vector<int> myInputVector{1, 2, 3, 4, 5};
  int              result;

  result = std17::reduce(myInputVector.begin() ,
                         myInputVector.end()   );

  std::cout << result << " ";
  std::cout << std::endl;
  return 0;
}
// Output: 15

Reference: http://en.cppreference.com/w/cpp/algorithm/reduce

C++17: New Headers

C++17 added the following headers:

<any>
<execution>
<memory_resource>
<optional>
<string_view>
<variant>

Reference: http://en.cppreference.com/w/cpp/header

C++: SFINAE

SFINAE stands for “Substitution Failure is Not an Error”. When deducing which template function to use, if the compiler tries one template function, and if the substitution of template parameters is a problem; instead of the compiler declaring an error and stopping, the compiler tries the remaining template functions.

References:

http://en.cppreference.com/w/cpp/language/sfinae

https://en.wikipedia.org/wiki/Substitution_failure_is_not_an_error

C++17: std::gcd() and std::lcm()

C++17 added the greatest common divisor (GCD) function and the least common multiple (LCM) function.

#include 
#include 

int main()
{
  std::cout << std::gcd( 0, 10) << " "; // 10 
  std::cout << std::gcd( 1, 10) << " "; //  1
  std::cout << std::gcd( 2, 10) << " "; //  2
  std::cout << std::gcd( 3, 10) << " "; //  1
  std::cout << std::gcd( 4, 10) << " "; //  2
  std::cout << std::gcd( 5, 10) << " "; //  5
  std::cout << std::gcd( 6, 10) << " "; //  2
  std::cout << std::gcd( 7, 10) << " "; //  1
  std::cout << std::gcd( 8, 10) << " "; //  2
  std::cout << std::gcd( 9, 10) << " "; //  1
  std::cout << std::gcd(10, 10) << " "; // 10

  std::cout << ": ";

  std::cout << std::lcm( 0, 10) << " "; //  0 
  std::cout << std::lcm( 1, 10) << " "; // 10
  std::cout << std::lcm( 2, 10) << " "; // 10
  std::cout << std::lcm( 3, 10) << " "; // 30
  std::cout << std::lcm( 4, 10) << " "; // 20
  std::cout << std::lcm( 5, 10) << " "; // 10
  std::cout << std::lcm( 6, 10) << " "; // 30
  std::cout << std::lcm( 7, 10) << " "; // 70
  std::cout << std::lcm( 8, 10) << " "; // 40
  std::cout << std::lcm( 9, 10) << " "; // 90
  std::cout << std::lcm(10, 10) << " "; // 10

  std::cout << std::endl;
  return 0;
}
// Output: 10 1 2 1 2 5 2 1 2 1 10 : 0 10 10 30 20 10 30 70 40 90 10

References:
http://en.cppreference.com/w/cpp/numeric/gcd
http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p0295r0.pdf

C++17: C++17 is based on C11 instead of C99.

C++17 is based on C11 instead of C99.

Reference: http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p0063r2.html

C++17: std::clamp()

C++17 added the template function std::clamp() is a combination of std::max() and std::min(). Here is an example:

#include <algorithm>
#include <iostream>

int main()
{
  //                      Value Min Max
  std::cout << std::clamp( 5   ,  0, 10) << " "; //  5
  std::cout << std::clamp(-5   ,  0, 10) << " "; //  0
  std::cout << std::clamp(20   ,  0, 10) << " "; // 10

  std::cout << std::endl;
  return 0;
}
// Output: 5 0 10

Reference: https://stackoverflow.com/questions/38060436/what-are-the-new-features-in-c17

C++17: The register keyword was removed.

C++17 removed the register keyword. This keyword used to be used to hint to the compiler that a local variable is used so much that it would be nice to use a CPU Register for it instead of the stack.

Reference: http://www.bfilipek.com/2017/01/cpp17features.html#remove-deprecated-use-of-the-register-keyword