arrays of pointers to function?????

Hi all, I'm new to this board and C++, I'm writing a piece of code that uses arrays of pointers to function. The program contains a menu-driven interface. and there are five options, each them contains a certain function.

I wrote the following code, but it won't work and everytime i compile it ,it keeps telling me missing ")" before int...

Any ideas? Thx!

Code:

#include <iostream>

using std::cout;
using std::endl;
using std::cin;
using std::fixed;
using std::left;

#include <iomanip>

using std::setw;
using std::setprecision;

const int students = 3;
const int exams = 4;

//function prototypes
void printArray(int [][exams],int,int);
void minimum(int [][exams],int,int);
void maximum(int [][exams],int,int);
void average(int [][exams],int,int);

int main()
{
	//initialize student grades for three students (rows)
	int stduentGrades[students][exams]=
	{	{77,68,86,73},
		{96,87,89,78},
		{70,90,86,81}	};

	//initialize array of 4 pointers to functions that each
	//takes an array and two integers argument and return nothing

	void (*processGrades[4])(int [][exams], int, int) = {printArray,minimum,maximum,average};


	int choice;

	cout<<"Enter a choice:\n"
		<<"0  Print the array of grades\n"
		<<"1  Find the minimum grade\n"
		<<"2  Find the maximum grade\n"
		<<"3  Print the average on all test for each student\n"
		<<"4  End program\n"<<endl;
	cin>>choice;
	
	//process user's choice
	while ( choice >= 0 && choice <4 ){

		//invoke function at location choice in array 
		//and pass studentgarde array, students and exams as an argument
	(*processGrades[choice]) (int studentGrades[students][exams], int students, int exams);
	
		cout<<"Enter a choice:\n"
			<<"0  Print the array of grades\n"
			<<"1  Find the minimum grade\n"
			<<"2  Find the maximum grade\n"
			<<"3  Print the average on all test for each student\n"
			<<"4  End program\n"<<endl;
		cin>>choice;
	}

	cout<<"Program execution completed."<<endl;

	return 0; //indicates successful termination

}//end main

void printArray( int studentGrades[students][exams],int students,int exams)
{
    cout << left << "                 [0]  [1]   [2]   [3]";
	// output grades in tablual format
	for(int i=0; i<students; i++){

		//output lable for row
		cout << "\nstudentGrade[" <<i <<"]";

		//output one grades for one student
		for (int j=0; j<exams; j++)

			cout << setw(5)<<studentGrades[i][j];

	}//end outer for

}//end function printArray

void minimum(int studentGrades[students][exams],int students,int exams)
{
	int lowGrade = 100; //initialize to highest possible grade

	for ( int i=0; i<students; i++)

		for (int j=0; j<exams; j++)

			if ( studentGrades[i][j] < lowGrade)

				lowGrade = studentGrades[i][j];

	cout <<"Lowest Grade is "<< lowGrade<<endl;
}

void maximum(int studentGrades[students][exams],int students,int exams)
{
	int highGrade = 0; //initialize to lowest possible grade

	for ( int i=0; i<students; i++)

		for (int j=0; j<exams; j++)

			if ( studentGrades[i][j] > highGrade)

				highGrade = studentGrades[i][j];

	cout <<"Highest Grade is "<< highGrade<<endl;
}

void average(int studentGrades[students][exams],int students,int exams)
{
	int i=0;
	while(i<students){

		int sum =0;//initialize sum to 0
		double avg = 0.00; //initialize avarage to 0

			for (int j=0; j<exams; j++)

				sum += studentGrades[i][j];

				avg = static_cast<double>(sum)/exams;

				cout <<"The average grade for student"<<i<<"is"
					<<fixed<<setprecision(2)<<avg<<endl;
		i++;
	}//end while loop

}

Code:

		//invoke function at location choice in array 
		//and pass studentgarde array, students and exams as an argument
	(*processGrades[choice]) (int studentGrades[students][exams], int students, int exams);

Strip away all the declaration fluff - it's no different from calling any other function

Code:

	//invoke function at location choice in array 
	//and pass studentgarde array, students and exams as an argument
	processGrades[choice](studentGrades, students, exams);

Thx salem . I followed your instruction, but the error comes again.
error C2065: 'studentGrades' : undeclared identifier

I have declared "studentGrades" in Main, what's wrong with my code, ANY ONE? HELP!

> stduentGrades
Try spelling your variables consistently (or correctly) then

It appears you have a few bugs in there.


I've debugged it for you. Mostly, what I did was changed your main a bit and put *int* instead of void for your function definitions.

Also your the title for your array was fubar. lol

Code:

#include <iostream>

using std::cout;
using std::endl;
using std::cin;
using std::fixed;
using std::left;

#include <iomanip>

using std::setw;
using std::setprecision;

const int students = 3;
const int exams = 4;

//function prototypes
int printArray(int [][exams],int,int);
int minimum(int [][exams],int,int);
int maximum(int [][exams],int,int);
int average(int [][exams],int,int);

int main()
{
	//initialize student grades for three students (rows)
	int studentGrades[students][exams]=
	{	{77,68,86,73},
		{96,87,89,78},
		{70,90,86,81}	};
	
		

	//initialize array of 4 pointers to functions that each
	//takes an array and two integers argument and return nothing

	//void (*processGrades[4])(int [][exams], int, int) = {printArray,minimum,maximum,average};


	int choice;

	cout<<"Enter a choice:\n"
		<<"0  Print the array of grades\n"
		<<"1  Find the minimum grade\n"
		<<"2  Find the maximum grade\n"
		<<"3  Print the average on all test for each student\n"
		<<"4  End program\n"<<endl;
	cin>>choice;
	if(choice==0)
	{
	    printArray(studentGrades,students,exams);
	}   
    if(choice==1)
    {
        minimum(studentGrades,students,exams);
    }
    if(choice==2)
    {
        maximum(studentGrades,students,exams);
    }
    if(choice==3)
    {
        average(studentGrades,students,exams);
    }             
	


	cout<<"Program execution completed."<<endl;
	int stop;
	cin>>stop;

	return 0; //indicates successful termination

}//end main

int printArray( int studentGrades[students][exams],int students,int exams)
{
    cout << left << "              [0]  [1]   [2]   [3]";
	// output grades in tablual format
	for(int i=0; i<students; i++){

		//output lable for row
		cout << "\nstudentGrade[" <<i <<"]";

		//output one grades for one student
		for (int j=0; j<exams; j++)

			cout << setw(5)<<studentGrades[i][j];

	}//end outer for

}//end function printArray

int minimum(int studentGrades[students][exams],int students,int exams)
{
	int lowGrade = 100; //initialize to highest possible grade

	for ( int i=0; i<students; i++)

		for (int j=0; j<exams; j++)

			if ( studentGrades[i][j] < lowGrade)

				lowGrade = studentGrades[i][j];

	cout <<"Lowest Grade is "<< lowGrade<<endl;
}

int maximum(int studentGrades[students][exams],int students,int exams)
{
	int highGrade = 0; //initialize to lowest possible grade

	for ( int i=0; i<students; i++)

		for (int j=0; j<exams; j++)

			if ( studentGrades[i][j] > highGrade)

				highGrade = studentGrades[i][j];

	cout <<"Highest Grade is "<< highGrade<<endl;
}

int average(int studentGrades[students][exams],int students,int exams)
{
	int i=0;
	while(i<students){

		int sum =0;//initialize sum to 0
		double avg = 0.00; //initialize avarage to 0

			for (int j=0; j<exams; j++)

				sum += studentGrades[i][j];

				avg = static_cast<double>(sum)/exams;

				cout <<"The average grade for student "<<i<<" is "
					<<fixed<<setprecision(2)<<avg<<endl;
		i++;
	}//end while loop

}

Hi treenef, Thanks for your help. (it works when i still use void as return type)
The problem is why (*processGrades[choice]) (int studentGrades[students][exams], int students, int exams);won't work?
Anyone who has experience with "arrays of pointers to function" can help. Please...
BTW, thanks salem, I have checked all "studentGrades" but no miss spelling, i tried you way, just won't work. Anyway thanks for you help.
Can anyone take a look at my code again please...

Code:

#include <iostream>

using std::cout;
using std::endl;
using std::cin;
using std::fixed;
using std::left;

#include <iomanip>

using std::setw;
using std::setprecision;

const int students = 3;
const int exams = 4;

//function prototypes
void printArray(int [][exams],int,int);
void minimum(int [][exams],int,int);
void maximum(int [][exams],int,int);
void average(int [][exams],int,int);

int main()
{
	//initialize student grades for three students (rows)
	int stduentGrades[students][exams]=
	{	{77,68,86,73},
		{96,87,89,78},
		{70,90,86,81}	};

	//initialize array of 4 pointers to functions that each
	//takes an array and two integers argument and return nothing

	void (*processGrades[4])(int [][exams], int, int) = {printArray,minimum,maximum,average};


	int choice;

	cout<<"Enter a choice:\n"
		<<"0  Print the array of grades\n"
		<<"1  Find the minimum grade\n"
		<<"2  Find the maximum grade\n"
		<<"3  Print the average on all test for each student\n"
		<<"4  End program\n"<<endl;
	cin>>choice;
	
	//process user's choice
	while ( choice >= 0 && choice <4 ){

		//invoke function at location choice in array 
		//and pass studentgarde array, students and exams as an argument
		(*processGrades[choice]) (int studentGrades[students][exams],int students,int exams);
	

		cout<<"Enter a number between 0 and 3, 4 to end: ";
		cin>>choice;
	}

	cout<<"Program execution completed."<<endl;

	return 0; //indicates successful termination

}//end main

void printArray( int studentGrades[students][exams],int students,int exams)
{
    cout << left << "                 [0]  [1]   [2]   [3]";
	// output grades in tablual format
	for(int i=0; i<students; i++){

		//output lable for row
		cout << "\nstudentGrade[" <<i <<"]";

		//output one grades for one student
		for (int j=0; j<exams; j++)

			cout << setw(5)<<studentGrades[i][j];

	}//end outer for

}//end function printArray

void minimum(int studentGrades[students][exams],int students,int exams)
{
	int lowGrade = 100; //initialize to highest possible grade

	for ( int i=0; i<students; i++)

		for (int j=0; j<exams; j++)

			if ( studentGrades[i][j] < lowGrade)

				lowGrade = studentGrades[i][j];

	cout <<"Lowest Grade is "<< lowGrade<<endl;
}

void maximum(int studentGrades[students][exams],int students,int exams)
{
	int highGrade = 0; //initialize to lowest possible grade

	for ( int i=0; i<students; i++)

		for (int j=0; j<exams; j++)

			if ( studentGrades[i][j] > highGrade)

				highGrade = studentGrades[i][j];

	cout <<"Highest Grade is "<< highGrade<<endl;
}

void average(int studentGrades[students][exams],int students,int exams)
{
	int i=0;
	while(i<students){

		int sum =0;//initialize sum to 0
		double avg = 0.00; //initialize avarage to 0

			for (int j=0; j<exams; j++)

				sum += studentGrades[i][j];

				avg = static_cast<double>(sum)/exams;

				cout <<"The average grade for student"<<i<<"is"
					<<fixed<<setprecision(2)<<avg<<endl;
		i++;
	}//end while loop

}

any one please help

Code:

The problem is why (*processGrades[choice]) (int studentGrades[students][exams], int students, int exams);won't work?

The reason why it doesn't work is because your syntax is all wrong.
When passing arrays into functions don't really need to use the '*' notation. As shown in my example.

As far as I can tell the rest of program appears to be ok. The only problem I think you have is actually *calling the function*. Read up on this!!

Secondly,

BTW, thanks salem, I have checked all "studentGrades" but no miss spelling

I don't think you have, notice anything wrong here?

Code:

int main()
{
	//initialize student grades for three students (rows)
	int stduentGrades[students][exams]=
	{	{77,68,86,73},
		{96,87,89,78},
		{70,90,86,81}	};

Oh and another thing, it's wise to put brackets in your *for loops* to clarify their parenthesis..

Does this do what you want? I've added the while loop, but I thought that was fairly simple?

Oh please, I fixed the two things I previously mentioned

Code:

#include <iostream>

using std::cout;
using std::endl;
using std::cin;
using std::fixed;
using std::left;

#include <iomanip>

using std::setw;
using std::setprecision;

const int students = 3;
const int exams = 4;

//function prototypes
void printArray(int [][exams],int,int);
void minimum(int [][exams],int,int);
void maximum(int [][exams],int,int);
void average(int [][exams],int,int);

int main()
{
	//initialize student grades for three students (rows)
	int studentGrades[students][exams]=  //!! FIXED!!! (as per previous comments)
	{	{77,68,86,73},
		{96,87,89,78},
		{70,90,86,81}	};

	//initialize array of 4 pointers to functions that each
	//takes an array and two integers argument and return nothing

	void (*processGrades[4])(int [][exams], int, int) = {printArray,minimum,maximum,average};


	int choice;

	cout<<"Enter a choice:\n"
		<<"0  Print the array of grades\n"
		<<"1  Find the minimum grade\n"
		<<"2  Find the maximum grade\n"
		<<"3  Print the average on all test for each student\n"
		<<"4  End program\n"<<endl;
	cin>>choice;
	
	//process user's choice
	while ( choice >= 0 && choice <4 ){

		//invoke function at location choice in array 
		//and pass studentgarde array, students and exams as an argument
//		(*processGrades[choice]) (int studentGrades[students][exams],int students,int exams);
		processGrades[choice](studentGrades,students,exams); //!! FIXED!!! (as per previous comments)


		cout<<"\nEnter a number between 0 and 3, 4 to end: "; //!! FIXED MINOR FORMATTING
		cin>>choice;
	}

	cout<<"Program execution completed."<<endl;

	return 0; //indicates successful termination

}//end main

void printArray( int studentGrades[students][exams],int students,int exams)
{
    cout << left << "                 [0]  [1]   [2]   [3]";
	// output grades in tablual format
	for(int i=0; i<students; i++){

		//output lable for row
		cout << "\nstudentGrade[" <<i <<"]";

		//output one grades for one student
		for (int j=0; j<exams; j++)

			cout << setw(5)<<studentGrades[i][j];

	}//end outer for

}//end function printArray

void minimum(int studentGrades[students][exams],int students,int exams)
{
	int lowGrade = 100; //initialize to highest possible grade

	for ( int i=0; i<students; i++)

		for (int j=0; j<exams; j++)

			if ( studentGrades[i][j] < lowGrade)

				lowGrade = studentGrades[i][j];

	cout <<"Lowest Grade is "<< lowGrade<<endl;
}

void maximum(int studentGrades[students][exams],int students,int exams)
{
	int highGrade = 0; //initialize to lowest possible grade

	for ( int i=0; i<students; i++)

		for (int j=0; j<exams; j++)

			if ( studentGrades[i][j] > highGrade)

				highGrade = studentGrades[i][j];

	cout <<"Highest Grade is "<< highGrade<<endl;
}

void average(int studentGrades[students][exams],int students,int exams)
{
	int i=0;
	while(i<students){

		int sum =0;//initialize sum to 0
		double avg = 0.00; //initialize avarage to 0

			for (int j=0; j<exams; j++)

				sum += studentGrades[i][j];

				avg = static_cast<double>(sum)/exams;

				cout <<"The average grade for student"<<i<<"is"
					<<fixed<<setprecision(2)<<avg<<endl;
		i++;
	}//end while loop

}

And got these results.

Code:

$ g++ hello.cpp
$ ./a.out
Enter a choice:
0  Print the array of grades
1  Find the minimum grade
2  Find the maximum grade
3  Print the average on all test for each student
4  End program

0
                 [0]  [1]   [2]   [3]
studentGrade[0]77   68   86   73
studentGrade[1]96   87   89   78
studentGrade[2]70   90   86   81
Enter a number between 0 and 3, 4 to end: 1
Lowest Grade is 68

Enter a number between 0 and 3, 4 to end: 2
Highest Grade is 96

Enter a number between 0 and 3, 4 to end: 3
The average grade for student0is76.00
The average grade for student1is87.50
The average grade for student2is81.75

Enter a number between 0 and 3, 4 to end: 4
Program execution completed.

The rest of the formatting you can fix yourself.

to both treenef and salem You guys are so great! Problem solved!!!!!