Passing a C++ vector to function

SnackMan78 · #1 18-Apr-2005, 09:03

What I'd like to do is create a C++ function that is passed a character array and a vector of long integers. What I'd like to know is how do I set up the Prototype, the Function definition and the actual call. I've tried the following without success (compiler errors):

the variables are defined as:

CPP / C++ / C Code:

	char inCharArry[100];
	vector<long> inVec;

Prototype:

CPP / C++ / C Code:

	void ProcessInput(const char *, vector<long>*);

Call to function:

CPP / C++ / C Code:

	ProcessInput(inCharArry, inVec);

Function definition:

CPP / C++ / C Code:

	template<long T>
	void ProcessInput(const char inChar[], vector<long>& invector)

Any help with this will be appreciated

davekw7x · #2 18-Apr-2005, 09:19

Quote:

Originally Posted by SnackMan78

What I'd like to do is create a C++ function that is passed a character array and a vector of long integers. What I'd like to know is how do I set up the Prototype, the Function definition and the actual call. I've tried the following without success (compiler errors):

Any help with this will be appreciated

The function declaration (prototype) must be exactly equivalent to the function definition.
You declared the second argument to be a pointer to a vector, but the definition has a reference to a vector.

Normally, you should post the exact error messages to let us know what you have seen so far, but I'll just give an example to show how it should work:

CPP / C++ / C Code:

#include <iostream>
#include <vector>

using std::cout;
using std::endl;
using std::vector;

int main()
{
  void ProcessInput(const char *, vector<long> *);

  char inCharArry[100];
  vector<long> inVec;

  cout << "Calling   function ProcessInput()" << endl;
  ProcessInput(inCharArry, &inVec);
  cout << "Back from function ProcessInput()" << endl;

  return 0;
}

void ProcessInput(const char inChar[], vector<long> *invector)
{
  cout<< "In function ProcessInput()" << endl;
}

Note that, for function arguments, "char *" and "char[]" are exactly equivalent, but "vector<long> &" and "vector<long> *" are really, realllllly different.

Regards,

Dave

SnackMan78 · #3 18-Apr-2005, 09:51

Thanks Dave for your response.

I plugged in your suggestion into my compiler MS Visual Sudio .NET 2003 (MS Visual C++), and got the following compiler error:

error C2783: 'void ProcessInput(const char *, std::vector<_Ty> *)' : could not deduce template argument for 'T' with [ _Ty=long ]

The line it is flagging is the function call:
ProcessInput(inCharArry, &inVec)

Hope this provides the missing pieces

davekw7x · #4 18-Apr-2005, 10:01

Quote:

Originally Posted by SnackMan78

Thanks Dave for your response.

I plugged in your suggestion into my compiler MS Visual Sudio .NET 2003 (MS Visual C++), and got the following compiler error:

error C2783: 'void ProcessInput(const char *, std::vector<_Ty> *)' : could not deduce template argument for 'T' with [ _Ty=long ]

The line it is flagging is the function call:
ProcessInput(inCharArry, &inVec)

Hope this provides the missing pieces

I'm not sure what you are doing with the template<>. Unless someone else can see what you are getting at, maybe you should post more code.

However, I would like to revisit my example.

You should erase the following comment from your life-experience memory:

Quote:

Originally Posted by davekw7x

Note that, for function arguments, "char *" and "char[]" are exactly equivalent

The statement is absolutely true for C, and most C++ compilers accept it, but strictly speaking you should make the definition match the declaration exactly. That's what it takes to get my example to compile with the .NET c++ compiler.

CPP / C++ / C Code:

int main()
{
  void ProcessInput(const char [], vector<long> *);

  char inCharArry[100];
  vector<long> inVec;

  ProcessInput(inCharArry, &inVec);

  return 0;
}

void ProcessInput(const char inChar[], vector<long> *invector)
{
  // all of the ProcessInput() stuff
}

Regards,

Dave

LuciWiz · #5 18-Apr-2005, 10:23

Quote:

Originally Posted by davekw7x

I'm not sure what you are doing with the template<>. Unless someone else can see what you are getting at, maybe you should post more code.

Indeed, I compiled and ran Dave's code without problems (well, I did add the definition of the function before the main, because my compiler asked for it). The problem lies somewhere else.

Please post the new code.

Regards,
Lucian

SnackMan78 · #6 18-Apr-2005, 12:53

Quote:

Originally Posted by davekw7x

I'm not sure what you are doing with the template<>. Unless someone else can see what you are getting at, maybe you should post more code.

However, I would like to revisit my example.

You should erase the following comment from your life-experience memory:

The statement is absolutely true for C, and most C++ compilers accept it, but strictly speaking you should make the definition match the declaration exactly. That's what it takes to get my example to compile with the .NET c++ compiler.

CPP / C++ / C Code:

int main()
{
  void ProcessInput(const char [], vector<long> *);

  char inCharArry[100];
  vector<long> inVec;

  ProcessInput(inCharArry, &inVec);

  return 0;
}

void ProcessInput(const char inChar[], vector<long> *invector)
{
  // all of the ProcessInput() stuff
}

Regards,

Dave

CPP / C++ / C Code:

/* 
After compiling this, I get the error msg:
   [i][b]error C2228: left of '.push_back' must have class/struct/union type[/b][/i]
*/
 
//A better way to describe my intentions is that once I get the vector into 
//the ProcessInput function,  I want to populate the vector with values, and 
//have those values available when I leave the function for further processing.
//
//Since the vector dot.modifiers do not work on  my *inVector, I did not 
//explain my intentions clearly enough, and I described the  incorrect usage.  
//
//Ultimately, once I understand what I'm doing, I will change inCharArry to a 
//vector<char>, and let the User input as long a string as they desire
//
//I've ripped out everything associated with this program except what is 
//necessary for my problem. The template<T> reference is gone too
//

#include <iostream>
#include <vector>   
   using namespace std;

void ProcessInput(const char [], vector<long> *);
int conv2integer(char);

int main()
{	
	char inCharArry[100];
	vector<long> inVec;

	cout<<"\nEnter your first value: ";
	cin >> inCharArry;

	cout<<"\nThe input is: " << inCharArry;
	cout<<"\nThe numeric-only edited data is: \n";

	ProcessInput(inCharArry, &inVec);

  cout<<"\n";
  return 0;
}

void ProcessInput(const char inputVal[], vector<long> *inVector)
{
	int i = 0,
		nbr = 0;
	vector<long> inVec;

	while (inputVal[i] != '\0')
	{
		if(isdigit(inputVal[i]))
		{
			cout<< inputVal[i];
			nbr = conv2integer(inputVal[i]);	// convert the ascii input to integer values
			inVector.push_back(nbr);			//load vector with ONLY numeric input values
		}

	i++;

	}		// end while
}

int conv2integer(char inChar)
{
// Convert the ascii char to an integer, char function "atoi" does not work for this case. This is my work around

	switch(inChar)
	{
		case 49:
			return 1;
		case 50: 
			return 2;
		case 51:
			return 3;
		case 52:
			return 4;
		case 53:
			return 5;
		case 54:
			return 6;
		case 55:
			return 7;
		case 56:
			return 8;
		case 57:
			return 9;
		default:
			return 0;
	}
}

LuciWiz · #7 18-Apr-2005, 13:00

You pass the vector as a pointer. You can't call a method on a pointer to an object with .(dot). You need to use the -> construct:

CPP / C++ / C Code:

//inVector.push_back(nbr);      // wrong
inVector->push_back(nbr);      //load vector with ONLY numeric input values

Regards,
Lucian

SnackMan78 · #8 18-Apr-2005, 13:29

Quote:

Originally Posted by LuciWiz

You pass the vector as a pointer. You can't call a method on a pointer to an object with .(dot). You need to use the -> construct:

CPP / C++ / C Code:

//inVector.push_back(nbr);      // wrong
inVector->push_back(nbr);      //load vector with ONLY numeric input values

Regards,
Lucian

That's the info I needed!!!

I plugged in the "->" code, and the function is doing exactly what I want.

Thank-you LuciWiz for your answer, and davekw7x, thanks for your help and quick response in getting me to my goal--- James

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