I am trying to use the sleep_for function from the example here (http://stackoverflow.com/a/9747668), but when I try to use it, I always keep getting errors

3ds_main_sillyprogram.cpp

#include <3ds.h>
#include <stdio.h>
#include <chrono>
#include <thread>
#include <iostream>

using namespace std;
using namespace std::this_thread; // sleep_for, sleep_until
using namespace std::chrono_literals; // ns, us, ms, s, h, etc.
using std::chrono::system_clock;

// Prototypes
void AddDonationAmount(float total, float &donate, float amount);
void GreetingMessage(float total, float donate, float amount);
void Nintendo3DSScreenStuff();
void StateResults(float total, float donate);
void SubtractDonationAmount(float total, float &donate, float amount);
bool ValdiateAmount(float total, float donate);


int main(int argc, char **argv)
{
	float totalBalance = 10000, donateAmount = 0, modifyAmount = 1000;

	//Initialize gfx (note: not needed if you're using SF2Dlib)
	gfxInitDefault();
	consoleInit(GFX_TOP, NULL);

	GreetingMessage(totalBalance, donateAmount, modifyAmount);

	// Main loop
	while (aptMainLoop())
	{
		//Scan all the inputs. This should be done once for each frame
		hidScanInput();
		u32 kDown = hidKeysDown();

		if (kDown & KEY_A)
		{
			AddDonationAmount(totalBalance, donateAmount, modifyAmount);
			consoleClear();
			GreetingMessage(totalBalance, donateAmount, modifyAmount);
		}

		else if (kDown & KEY_B)
		{
			SubtractDonationAmount(totalBalance, donateAmount, modifyAmount);
			consoleClear();
			GreetingMessage(totalBalance, donateAmount, modifyAmount);
		}

		else if (kDown & KEY_START)
		{
			StateResults(totalBalance, donateAmount);
			sleep_for(2s);
			break;
		}

		Nintendo3DSScreenStuff();
	}

	gfxExit();
	return 0;
}




void AddDonationAmount(float total, float &donate, float amount)
{
	float donateTemp = donate;
	donateTemp += amount;
	
	if (ValdiateAmount(total, donateTemp))
	{
		donate = donateTemp;
	}
	
	else
	{
		cout << "You don't have enough money in your wallet." << endl;
		//sleep_for(2s);
	}
	
}




void GreetingMessage(float total, float donate, float amount)
{
	cout << "Welcome to the Children With No Life Foundation. We dedicate ourselves "
		 << "with helping children who have no social life what so ever, so that they "
		 << "can be more like the other cool kids who do have a life." << endl
		 << endl << endl;

	cout << "How much would you like to donate?" << endl
	     << "\tYou currently have " << total << " dollars in you wallet" << endl
	     << "\tYour donation amount is currently " << donate << endl
	     << endl;

	cout << "Press A to add " << amount <<" dollars" << endl
		 << "Press B to remove " << amount << " dollars" << endl
		 << "Press Start to send the money and exit the program" << endl;
}




void Nintendo3DSScreenStuff()
{
	// Flush and swap framebuffers, this is needed for rendering these will not be needed when using SF2D lib
	gfxFlushBuffers();
	gfxSwapBuffers();

	//Wait for VBlank, this is needed for rendering these will not be needed when using SF2D lib
	gspWaitForVBlank();
}




void StateResults(float total, float donate)
{
	double percentage;
	percentage = donate/total;

	if (percentage > .50)
	{
		cout << "Wow! Thank you so much for your donation! "
			 << "We will have a picture of you hanged on our wall!"
			 << endl;
	}

	else if (percentage < .0075)
	{
		cout << "Every little bit counts!" << endl;
	}

	else if (percentage < .15)
	{
		cout << "Thank you for your contribution" << endl;
	}

	else if (percentage < .25)
	{
		cout << "That's pretty nice of you";
	}

	else if (percentage <= .50)
	{
		cout << "That is a good amount money you have donated. "
			 << "Thank you for your contribution."
			 << endl; 
	}

	else if (percentage == 0)
	{
		cout << "I see..." << endl;
	}

	cout << "Sending you back to the homebrew menu" << endl;
}




void SubtractDonationAmount(float total, float &donate, float amount)
{
	float donateTemp = donate;
	donateTemp -= amount;
	
	if (ValdiateAmount(total, donateTemp))
	{
		donate = donateTemp;
	}
	
	else
	{
		cout << "Donation amount is set to zero" << endl;
		//sleep_for(2s);
	}
}




bool ValdiateAmount(float total, float donate)
{
	if (donate > total)
	{
		return false;
	}

	else if (donate < 0)
	{
		return false;
	}

	else
	{
		return true;
	}
}