Round Function

[OldRon]

OK guys, take it easy because this is my 1st program. I have jumped some hurdles and resisted the urge to ask for help but the round function has me stumped. In the code below I had to create my own round function. Why won't (51199.9488-round(51199.9488)) return .0512? The debug error states that round is an undeclared identifier.

// First.cpp: Need I state more?

#include <stdafx.h>
#include <iostream>

using namespace std;

void main()
{
  double degrees=360;
  double poserr=0;
  double pulses=0;

  for (degrees=359; degrees<360;)
  {
     pulses=(((degrees*3600)/2.34375)+poserr); // Throw the previous error back into the grinder.

    if ((pulses-int(pulses))>=.5) // Rooky Round Function
	{
	  poserr=(pulses-int(pulses+1)); 
          pulses=int(pulses+1);
	}
    else if (pulses-int(pulses)<.5)
	{
	  poserr=(pulses-int(pulses)); 
          pulses=int(pulses);
	}

    std::cout << "Command: " << degrees;
    std::cout << " - Output: " << ((pulses/3600)*2.34375);
    std::cout << " - Pulses: " << pulses;
    std::cout << " - Error: " << ((poserr/3600)*2.34375);
    std::cout << "\n";
    std::cout << "\n";

    degrees=(degrees+.01);
  }

  std::cin.get();
}

[2kaud]

To use round(), you need to insert

#include <cmath>

at the top of the program as this include has the definition for the round() function.

Also

degrees = (degrees + .01);

can be removed and incorporated into the for statement as:

for (degrees = 359.0; degrees < 360.0; degrees += 0.01)

when dealing with non-integer constants, it is better to explicitly specify this by using a . in the number. So 350 becomes 359.0 and 360 becomes 360.0 etc.

Also, if (pulses - int(pulses)) is not >= .5 then it must be < .5, so the second if statement is not required.

if ((pulses - int(pulses)) >= .5) // Rooky Round Function
{
    poserr = (pulses - int(pulses + 1)); 
    pulses = int(pulses + 1);
}
else
{
    poserr = (pulses - int(pulses)); 
    pulses = int(pulses);
}

As you have using namespace std; after the #include statements, your std::cout statements do not need the std:: part and can be just cout

cout << "Command: " << degrees;

2.34375 must 'mean something' in the context of this program, so it would be good practice to specify this value as a const variable at the top of the program and use this const variable instead of the number in the code.

const double special = 2.34375;
int main()
....
pulses = (((degrees * 3600) / special) + poserr);

Also note that the correct format for main() is

int main()

although the main() function doesn't have to explicitly return a value as 0 is used if none is specified.

[OldRon]

OK, I included <cmath> and the error still exists. error C2065: 'round' : undeclared identifier

I created an APP in vb6 that performs a recursive folder/subfolder search, reads the folder files, and searches for a string. Starting in the VC98 folder there is no 'round'. Google has a lot of hits on that error and no solutions other than creating your own function. If I had a better understanding of the libraries then I could probably add my rounding function to math.h but I won't live long enough to reach that skill level so I'll be content with my rounding code. I have a lot to learn but I was surprised by how quickly I went from std::cout << "Hello World!" outputting the results that I need. That stupid lesson was where I threw the MS book in the trash when I was learning vb6. I appreciate your advice on the for statement and the unnecessary conditional statement.

Ron

[2kaud]

Starting in the VC98 folder

Ah. You are using C++98. That explains the issue. In C++, round() was added in the later C++11 release. C++98 is now 22 years old and there has been a lot of changes to the C++ language since then. The latest version is C++17 - with C++20 due for release shortly. Why not upgrade to the latest free VC2019 Community edition - which includes C++17? See https://visualstudio.microsoft.com/downloads/

PS For learning C++ on line, have a look at https://www.learncpp.com/

[OldRon]

Ah. You are using C++98. That explains the issue. In C++, round() was added in the later C++11 release. C++98 is now 22 years old and there has been a lot of changes to the C++ language since then. The latest version is C++17 - with C++20 due for release shortly. Why not upgrade to the latest free VC2019 Community edition - which includes C++17? See https://visualstudio.microsoft.com/downloads/

PS For learning C++ on line, have a look at https://www.learncpp.com/

My use is for entertainment and my wife would say that doesn't warrant the expense of buying a new programming suite... and she's always right.

[2kaud]

My use is for entertainment and my wife would say that doesn't warrant the expense of buying a new programming suite... and she's always right.

But VS2019 Community is free as I said in post #4

[2kaud]

Although round() is a C++11 feature, there are 2 similar ones in C++98 which might be helpful:

ceil() - which rounds upwards, returning the smallest integral value that is not less than
floor() - which rounds downwards, returning the largest integral value that is not greater than.

[OldRon]

Although round() is a C++11 feature, there are 2 similar ones in C++98 which might be helpful:

ceil() - which rounds upwards, returning the smallest integral value that is not less than
floor() - which rounds downwards, returning the largest integral value that is not greater than.

I had tried those functions but it was simpler to use (value - int(value)) + 1 if the fractional part was .5 or greater. I had Visual Studio 2010 Express on my drive so I installed it thinking that it would have round but that wasn't the case. It is the no license version but it required a serial key and MS let that page expire. After three chat sessions with MS it looked hopeless but I eventually found it without having to risk a download. I can run it in Windows 10 whereas the old software required a virtual XP machine. It would not not compile the simple program that it loaded when starting a new project. I don't know what it is but incremental compiling was the problem. I'm currently trying to learn about strings and it's sure a mess compared to vb6. My current project requires C++ so I'm eager to learn the programming language.

Thanks for your help,
Ron

[Arjay]

I had tried those functions but it was simpler to use (value - int(value)) + 1 if the fractional part was .5 or greater. I had Visual Studio 2010 Express on my drive so I installed it thinking that it would have round but that wasn't the case. It is the no license version but it required a serial key and MS let that page expire. After three chat sessions with MS it looked hopeless but I eventually found it without having to risk a download. I can run it in Windows 10 whereas the old software required a virtual XP machine. It would not not compile the simple program that it loaded when starting a new project. I don't know what it is but incremental compiling was the problem. I'm currently trying to learn about strings and it's sure a mess compared to vb6. My current project requires C++ so I'm eager to learn the programming language.

Thanks for your help,
Ron

If the old link to the 9 year old VC 2010 is no longer available it just might be a hint from MS to go to something newer - like the FREE version of VC 2019.

[2kaud]

I had Visual Studio 2010 Express on my drive so I installed it thinking that it would have round but that wasn't the case

VS 2010 is based upon C++98 - as C++11, which is needed for the round function, didn't exist at that point.

As you're using Windows 10, installing the free VS 2019 Community should be a no-brainer!

[OldRon]

If the old link to the 9 year old VC 2010 is no longer available it just might be a hint from MS to go to something newer - like the FREE version of VC 2019.

Of course you are right. If I'm going to learn C++ then I just as well be current.