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Problem passing function as a parameter?

Aim4Erudite (84)
Cant seem to figure out why I can't pass my function as a parameter and I have to use this program for future programs. By the end of this week I have to not only figure out that problem but convert the struct to a class among other things. Any help would be greatly appreciated... Thank you in advance for any help.

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 /* *** Statistical Analysis Program I ***   */


#include<iostream>
#include<fstream>
#include<string>
#include<cstring>

using namespace std;

const int arraySize = 50;

struct stat_list
{
	double list[arraySize];
	int length;
	int maxSize;
	double median;

};
// Function Prototype
stat_list file_Sort(stat_list stat_vals2);
void printArray_N_store((*file_Sort)(stat_list test_vals3));
void median_Of_Array((*file_Sort)(stat_list test_vals4));

int main()
{
	//variables
	string fileName;
	ifstream inFile;
	ofstream outFile;
	stat_list stat_vals;
	stat_vals.length = 0;
	stat_vals.maxSize = 50;

	//Infile loop
	do
	{
		cout << "Enter file name that contains the data to be sorted: \n";
		cin >> fileName;
		inFile.open(fileName.c_str());
		if (!inFile.is_open())
		{
			cout << "Error opening " << fileName << ", please try again \n";
		}
	} while (!inFile.is_open());

	//Outfile loop
	do
	{
		cout << "Enter the name of the file to store the sorted numbers: \n";
		cin >> fileName;
		outFile.open(fileName.c_str());
		if (!outFile.is_open())
		{
			cout << "Error opening " << fileName << ", please try again \n";
		}
	} while (!outFile.is_open());

	//filling array with values
	
	inFile >> stat_vals.list[stat_vals.length];
	while (inFile && stat_vals.length < stat_vals.maxSize) {
		stat_vals.length++;
		inFile >> stat_vals.list[stat_vals.length];
	}

	//Sort array
	file_Sort(stat_vals);
	printArray_N_store((&file_Sort)(stat_vals));
	median_Of_Array((&file_Sort)(stat_vals));

	outFile.close();
	inFile.close();

	return 0;
}

stat_list file_Sort(stat_list test_vals2)
{
	//Sorting
	int min;
	double temp;
	for (int i = 0; i < test_vals2.length - 1; i++)
	{
		min = i;
		for (int j = i + 1; j < test_vals2.length; j++)
		{
			if (test_vals2.list[j] < test_vals2.list[min])
				min = j;
		}
		if (min != i)
		{
			temp = test_vals2.list[i];
			test_vals2.list[i] = test_vals2.list[min];
			test_vals2.list[min] = temp;
		}
	}
	return test_vals2;
}
void printArray_N_store((*file_Sort)(stat_list test_vals3)){
	ifstream outfile;
	for (int a = 0; a < test_vals3.length; a++){
		outfile >> test_vals3.list[a] >> " ";
		cout << test_vals3.list[a] << " ";
		if (a % 10 == 0 && a != 0)cout << endl;
	}

}
/*
if the if statement prints out a 0 use the following

for (int p = 1; p < stat_vals.length; p++){
cout << stat_vals.list[p - 1] << " ";
if (p % 10 == 0 && p != 0)cout << endl;
}
*/

void median_Of_Array((*file_Sort)(stat_list test_vals4)){

	int m1, m2;
	double sum;
	m1 = (1 / 2)*(test_vals4.length);
	m2 = m1 + 1;

	sum = (test_vals4.list[m1]) + (test_vals4.list[m2]);
	test_vals4.median = sum / 2;
	cout << "The median of the array is: " << test_vals4.median << endl;

}
Last edited on
giblit (3750)
Why are you passing a function as a parameter? Why not just call the function?

Ps if you are going to pass as a function you need a std::function or void pointer as far as I was aware but still doesn't make sense.
Last edited on
Aim4Erudite (84)
Im not completely sure I understand you. I did call the function and the reason Im using a function as a parameter is to take the return value from the function without creating a separate variable. Although I tried that as well and I couldn't get to work that way either. Are you saying that a user defined function can't be use as a parameter?
coder777 (8444)
As giblit stated: you really don't need the function as a parameter.

You defined it wrong:
void printArray_N_store((*file_Sort)(stat_list test_vals3));
-> void printArray_N_store(stat_list (*file_Sort)(stat_list test_vals3));

printArray_N_store((&file_Sort)(stat_vals));
-> printArray_N_store(&file_Sort);


What you want is this:
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stat_list file_Sort(stat_list stat_vals2);
void printArray_N_store(const stat_list &sl); // Note: Not the function but result

int main()
{
...
	printArray_N_store(file_Sort(stat_vals));
Last edited on
appi (15)
I have modified your code Aim4Erudite...hope you find it useful.apologies if it not worked properly.

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 /* *** Statistical Analysis Program I ***   */


#include<iostream>
#include<fstream>
#include<string>
#include<cstring>

using namespace std;

const int arraySize = 50;

struct stat_list
{
	char list[arraySize];
	int length;
	int maxSize;
	double median;

};
// Function Prototype

stat_list file_Sort(stat_list test_vals2)
{
	//Sorting
	int min;
	double temp;
	for (int i = 0; i < test_vals2.length - 1; i++)
	{
		min = i;
		for (int j = i + 1; j < test_vals2.length; j++)
		{
			if (test_vals2.list[j] < test_vals2.list[min])
				min = j;
		}
		if (min != i)
		{
			temp = test_vals2.list[i];
			test_vals2.list[i] = test_vals2.list[min];
			test_vals2.list[min] = temp;
		}
	}
	return test_vals2;
}

stat_list printArray_N_store(stat_list test_vals3){
	ifstream outfile;
	for (int a = 0; a < test_vals3.length; a++){
	outfile >> test_vals3.list[a];
		cout << test_vals3.list[a];
		if (a % 10 == 0 && a != 0)cout << endl;
	}
	return test_vals3;
}

stat_list median_Of_Array(stat_list test_vals4){

	int m1, m2;
	double sum;
	m1 = (1 / 2)*(test_vals4.length);
	m2 = m1 + 1;
	sum = (test_vals4.list[m1]) + (test_vals4.list[m2]);
	test_vals4.median = sum / 2;
	cout << "The median of the array is: " << test_vals4.median << endl;
	
	return test_vals4;
}

int main()
{
	//variables
	string fileName;
	ifstream inFile;
	ofstream outFile;
	stat_list stat_vals;
	stat_vals.length = 0;
	stat_vals.maxSize = 50;

	//Infile loop
	do
	{
		cout << "Enter file name that contains the data to be sorted: \n";
		cin >> fileName;
		inFile.open(fileName.c_str());
		if (!inFile.is_open())
		{
			cout << "Error opening " << fileName << ", please try again \n";
		}
	} while (!inFile.is_open());

	//Outfile loop
	do
	{
		cout << "Enter the name of the file to store the sorted numbers: \n";
		cin >> fileName;
		outFile.open(fileName.c_str());
		if (!outFile.is_open())
		{
			cout << "Error opening " << fileName << ", please try again \n";
		}
	} while (!outFile.is_open());

	//filling array with values
	
	inFile >> stat_vals.list[stat_vals.length];
	while (inFile && stat_vals.length < stat_vals.maxSize) {
		stat_vals.length++;
		inFile >> stat_vals.list[stat_vals.length];
	}

	//Sort array
	file_Sort(stat_vals);
	printArray_N_store(stat_vals);
	median_Of_Array(stat_vals);

	outFile.close();
	inFile.close();

	return 0;
}
Aim4Erudite (84)
Im sorry guys Im trying all of the things your telling me to the best of my ability and I keep getting the following:
- Im using Visual Studio and Ive even tried on a separate IDE (called EBE) provided by the school and no luck.
This is the first error with the visual studio,

source.cpp(74): error C2664: 'void printArray_N_store(stat_list (__cdecl *)(stat_list))' : cannot convert argument 1 from 'stat_list' to 'stat_list (__cdecl *)(stat_list)'
No user-defined-conversion operator available that can perform this conversion, or the operator cannot be called
Last edited on
kbw (9488)
There's an easy way to make up a typedef that matches a given function. Say we want to make up a typedef for:
 
 
stat_list file_Sort(stat_list stat_vals2);
it would be:
 
 
typedef stat_list file_Sort_t(stat_list stat_vals2);


There's one detail we need to look at before we define printArray_N_store is the function it takes takes a parameter itself, a stat_list passed by value. So we need to pass that parameter in too, but we'll pass it in by const ref.

So the definition of printArray_N_store becomes:
 
 
void printArray_N_store_t(file_Sort_t* func, const stat_list& arg);


The code that uses those definitions become:
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int main()
{
	// ...
	printArray_N_store(file_Sort, stat_vals);
	// ...
}

void printArray_N_store(file_Sort_t* func, const stat_list& arg)
{
	stat_list test_vals3 = func(arg);

	ifstream outfile(/* need a filename */);
	for (size_t a = 0; a != test_vals3.length(); ++a)
	{
		outfile >> test_vals3.list[a] >> " ";
		cout << test_vals3.list[a] << " ";
		if (a % 10 == 0 && a != 0)
			cout << endl;
	}
}

Last edited on
Aim4Erudite (84)
Thank you all for your help, I apologize for the late response. Im in the last two week of summer school and they are laying it on thick. Also I have a two year old and five year old, so I don't have much free time. I plan to use your advice tomorrow. Thank you all again.
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