Weird template return value

[JRManx]

I am trying to make a function template that takes a "vector<T> v" as the parameter, and returns the total of all values in "v". It is supposed to be able to add ints, doubles, or strings, but I am having an issue.

So, when I try to run it (it compiles fine), I get this result:

   **** VECTOR PROGRAM MENU *********** 
   *                                  * 
   *    Choose a data type            * 
   *    for your vector:              * 
   *                                  * 
   *    1. Integer                    * 
   *    2. Double                     * 
   *    3. String                     * 
   *    0. Exit                       * 
   *                                  * 
   ************************************ 

Enter option number. 
: 1
How many integers do you want? 
: 1
Enter an integer to go into the vector. 
: 1
The total is: 91759646
Have a nice day!

My code (the relevant part) is:

template <typename T>
T accum (vector <T> v)
{
	T total;
	T x;
	
	if (v.empty())
	{
		return 0;
	}
	
	for (size_t i = 0; i < v.size(); ++i)
	{
		// I think the error is here, but I cna't figure out what it is
		x = v.at(i);
		total = total + x;
	}
	
	return total;
}

/*----------Main function--------------*/
/*=====================================*/
int main (int argc, char const *argv[])
{
	int option, size;
	
	//Accumulator adder;
	
	cout << endl
		 << "   **** VECTOR PROGRAM MENU *********** \n"
		 << "   *                                  * \n"
		 << "   *    Choose a data type            * \n"
		 << "   *    for your vector:              * \n"
		 << "   *                                  * \n"
		 << "   *    1. Integer                    * \n"
		 << "   *    2. Double                     * \n"
		 << "   *    3. String                     * \n"
		 << "   *    0. Exit                       * \n"
		 << "   *                                  * \n"
		 << "   ************************************ \n"
		 << "\nEnter option number. \n: ";
	cin >> option;
	
	switch (option)
	{
		case 1:
		{
			vector <int> list {};
			int number, total = 0;
			
			cout << "How many integers do you want? \n: ";
			cin >> size;
			
			for (size_t i = 0; i < size; ++i)
			{
				number = 0;
				cout << "Enter an integer to go into the vector. \n: ";
				cin >> number;
				list.push_back (number);
			}
			
			//adder.accum (list);
			total = accum (list);
			
			cout << "The total is: " << total << endl;
		}
		break;
	}
}

This isn't all the code, just the part I'm testing as of right now. If you want the rest, feel free to ask!

I believe that the error is in line 14, inside the function template, however I could be wrong. Also, the output number changes each time I run it. Maybe it has something to do with the address? Although the output wasn't in hexadecimal...I'm stumped.
Any help would be appreciated.
Thanks!
max

[lastchance]

You haven't initialised total (presumably, to 0) in accum

undefined + x = balderdash


Oh, I wish you wouldn't call a vector ... "list"!

[JRManx]

Yea I can't figure out how the heck to initialize "total". I tried "" but that didn't work, I tried "0", that didn't work either, I tried total = 0; but that didn't work either!!

And sorry about calling it "list" but that was just what came off the top of my head.

[Ganado]

In Python they're called lists, in Java they're called ArrayLists, in C# they're called Lists, in C++ they're called vectors... my personal opinion is that it's not a big deal that the variable is called 'list', as long as I know what type of collection it actually is.

[mbozzi]

Yea I can't figure out how the heck to initialize "total".

If you must, use value-initialization:
T total{};

A more flexible (generic) option is to pass "total" as an argument by value.

template <typename T> T accum(std::vector<T> v, T acc) 
{
  for (auto const& elt: v) acc = acc + elt;
  return acc;
}

A similar algorithm exists in the standard library as std::reduce, but if you require that elements are added in order, std::accumulate has you covered.

[ne555]

> Yea I can't figure out how the heck to initialize "total".
T total{};

[JRManx]

*facepalm* Why didn't I think of that. I hate OCD sometimes...makes you concentrate on some things so hard you completely forget about others. Part of it's because I use c++03 instead of c++11 (it's what I learned), but I really should have thought of that.

But thanks so much! I'll try that out and see if it works!
max

Edit:
It worked! Thanks @mbozzi, @ne555!

Oh, and just to show how dumb I can get, would you believe that I spent 15 minutes trying to figure out why setprecision() wasn't working, only to find that I was misspelling it? Just another of those little things.

[doug4]

Oh, and just to show how dumb I can get, would you believe that I spent 15 minutes trying to figure out why setprecision() wasn't working, only to find that I was misspelling it? Just another of those little things.

That sounds like programming to me.

[JRManx]

Yeah, I bet most of us have done that (or something similar) at one time or another.
Hmm...I think it would be fun to start a discussion in the Lounge about dumb things we've done while programming.