Technical facts

Operating system(s) or programming environment(s)

Lubuntu 15.04 (vivid)

IDE(s):

Qt Creator 3.1.1

Project type:

Console application

C++ standard:

C++98

Compiler(s):

G++ 4.9.2

Libraries used:

STL: GNU ISO C++ Library, version 4.9.2

Qt project file: ./CppStdEnable_ifExample1/CppStdEnable_ifExample1.pro


include(../../ConsoleApplication.pri) #Or use the code below

# QT += core

# QT += gui

# greaterThan(QT_MAJOR_VERSION, 4): QT += widgets

# CONFIG   += console

# CONFIG   -= app_bundle

# TEMPLATE = app

# CONFIG(release, debug|release) {

#   DEFINES += NDEBUG NTRACE_BILDERBIKKEL

# }

# QMAKE_CXXFLAGS += -std=c++11 -Wall -Wextra -Weffc++

# unix {

#   QMAKE_CXXFLAGS += -Werror

# }



include(../../Libraries/Boost.pri) #Or use the code below

# win32 {

#   INCLUDEPATH += \

#     ../../Libraries/boost_1_54_0

# }



SOURCES += main.cpp

./CppStdEnable_ifExample1/main.cpp


//Adapted from http://www.cplusplus.com/reference/type_traits/enable_if



// enable_if example: two ways of using enable_if

#include <iostream>

#include <type_traits>



// 1. the return type (bool) is only valid if T is an integral type:

template <class T>

typename std::enable_if<

  std::is_integral<T>::value,bool>::type

  is_odd(const T i)

{

  return static_cast<bool>(i%2);

}



// 2. the second template argument is only valid if T is an integral type:

template <class T,

  class = typename std::enable_if<std::is_integral<T>::value>::type>

bool is_even (T i)

{

  return !static_cast<bool>(i%2);

}



int main()

{

  const int i = 1; //code does not compile if type of i is not integral

  std::cout

    << "i is odd : " << is_odd(i) << '\n'

    << "i is even: " << is_even(i) << '\n';

}

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(C++) StdEnable_ifExample1

Technical facts

Qt project file: ./CppStdEnable_ifExample1/CppStdEnable_ifExample1.pro

./CppStdEnable_ifExample1/main.cpp