Homework assistance

•

What is DaniWeb IT Discussion Community?

You're currently browsing the C++ section within the Software Development category of DaniWeb, a massive community of 427,107 software developers, web developers, Internet marketers, and tech gurus who are all enthusiastic about making contacts, networking, and learning from each other. In fact, there are 2,097 IT professionals currently interacting right now! Registration is free, only takes a minute and lets you enjoy all of the interactive features of the site.

Join our community!

Please support our C++ advertiser: Programming Forums

Thread Tools Display Modes

Views: 987 | Replies: 8

•

Join Date: Nov 2006

Posts: 6

Reputation: solomon grundy is an unknown quantity at this point

Rep Power: 0

Solved Threads: 0

solomon grundy solomon grundy is offline

Offline

Newbie Poster

Homework assistance

Dec 11th, 2006

I need to construct a C++ program where I input from the screen the entries of two 3x3 matrices A and B. My program then computes A-5B. The matrices should be declared as two dimensional arrays.

What I have so far

 Help with Code Tags 
 cplusplus Syntax (Toggle Plain Text) 
#include <iostream>
 
using namespace std;
 
//Define the Matrix3X3 type.
typedef struct
{
float index[3][3];
} Matrix3X3;
 
//Function prototypes (functions are defined below main())
void printMatrix( Matrix3X3 a );
Matrix3X3 inputMatrix();
Matrix3X3 addMatrices( Matrix3X3 a, Matrix3X3 b );
Matrix3X3 subtractMatrices( Matrix3X3 a, Matrix3X3 b );
Matrix3X3 scalarMultiply( Matrix3X3 a, float scale );
 
//main() function
void main()
{
cout << "Please enter matrix A:" << endl;
 
Matrix3X3 A = inputMatrix();
 
cout << "Matrix A:" << endl;
 
printMatrix( A );
 
cout << "Please enter matrix B:" << endl;
 
Matrix3X3 B = inputMatrix () ;
 
cout << "Matrix B:" <
 
printMatrix ( B );
 
 
 
 
 
 
//The result I want is A - 5B.
//I can hold the result in a new matrix and print it out to complete the program.
 
}
 
void printMatrix( Matrix3X3 a )
{
//loop through rows
for( int i=0; i < 3; ++i )
{
//loop through column at each row
for( int j=0; j < 3; ++j )
{
//i is the row
//j is the column
float temp = a.index[i][j];
cout << temp << " ";
}
//go to the next line after each row
cout << endl;
}
}
 
Matrix3X3 inputMatrix()
{
Matrix3X3 temp;
 
//loop through rows
for( int i=0; i < 3; ++i )
{
//loop through column at each row
for( int j=0; j < 3; ++j )
{
//i is the row
//j is the column
cout << "Enter row " << i << " column " << j << ":" << endl;
cin >> temp.index[i][j];
}
}
 
return temp;
}
 
#include <iostream>
 
using namespace std;
 
//Define the Matrix3X3 type.
typedef struct
{
float index[3][3];
} Matrix3X3;
 
//Function prototypes (functions are defined below main())
void printMatrix( Matrix3X3 a );
Matrix3X3 inputMatrix();
Matrix3X3 addMatrices( Matrix3X3 a, Matrix3X3 b );
Matrix3X3 subtractMatrices( Matrix3X3 a, Matrix3X3 b );
Matrix3X3 scalarMultiply( Matrix3X3 a, float scale );
 
//main() function
void main()
{
cout << "Please enter matrix A:" << endl;
 
Matrix3X3 A = inputMatrix();
 
cout << "Matrix A:" << endl;
 
printMatrix( A );
 
cout << "Please enter matrix B:" << endl;
 
Matrix3X3 B = inputMatrix () ;
 
cout << "Matrix B:" <
 
printMatrix ( B );
 
 
 
 
 
 
//The result I want is A - 5B.
//I can hold the result in a new matrix and print it out to complete the program.
 
}
 
void printMatrix( Matrix3X3 a )
{
//loop through rows
for( int i=0; i < 3; ++i )
{
//loop through column at each row
for( int j=0; j < 3; ++j )
{
//i is the row
//j is the column
float temp = a.index[i][j];
cout << temp << " ";
}
//go to the next line after each row
cout << endl;
}
}
 
Matrix3X3 inputMatrix()
{
Matrix3X3 temp;
 
//loop through rows
for( int i=0; i < 3; ++i )
{
//loop through column at each row
for( int j=0; j < 3; ++j )
{
//i is the row
//j is the column
cout << "Enter row " << i << " column " << j << ":" << endl;
cin >> temp.index[i][j];
}
}
 
return temp;
}
 

How do I
1) Use the functions to calculate the result
2) And define the rest of the matrix.

Thanks

Last edited by ~s.o.s~ : Dec 11th, 2006 at 2:06 pm. Reason: Added code tags learn to use them yourself.

•

Join Date: May 2006

Location: Bellevue, WA

Posts: 1,548

Reputation: Infarction has a spectacular aura about

Rep Power: 8

Solved Threads: 51

Infarction Infarction is offline

Offline

Battle Programmer

Re: Homework assistance

Dec 11th, 2006

1) How would you do this if you were doing it by hand? Probably something like this:
- scale B by 5.
- subtract that matrix from A
2) what do you mean? It looks to me like you need to define subtractMatrices and scalarMultiply, but otherwise I don't understand what you need to define.

3) You do need to do the extra calls in main() to get the A-5B result.
4) You should use [code] tags when you post so we can read your code easily.

PS - it's int main() not void main()

Last edited by Infarction : Dec 11th, 2006 at 1:58 pm.

•

Join Date: Nov 2006

Posts: 6

Reputation: solomon grundy is an unknown quantity at this point

Rep Power: 0

Solved Threads: 0

solomon grundy solomon grundy is offline

Offline

Newbie Poster

Re: Homework assistance

Dec 12th, 2006

I'm still having trouble making this code work

Help with Code Tags

(Toggle Plain Text)

#include <iostream>
 
using namespace std;
 
//Define the Matrix3X3 type.
typedef struct
{
float index[3][3];
} Matrix3X3;
 
//Function prototypes (functions are defined below main())
void printMatrix( Matrix3X3 a );
Matrix3X3 inputMatrix();
Matrix3X3 addMatrices( Matrix3X3 a, Matrix3X3 b );
Matrix3X3 subtractMatrices( Matrix3X3 a, Matrix3X3 b );
Matrix3X3 scalarMultiply( Matrix3X3 a, float scale );
 
//main() function
void main()
{
cout << "Please enter matrix A:" << endl;
 
Matrix3X3 A = inputMatrix();
 
cout << "Matrix A:" << endl;
 
printMatrix( A );
 
cout << "Please enter matrix B:" << endl;
 
Matrix3X3 B = inputMatrix () ;
 
cout << "Matrix B:" <
 
printMatrix ( B );
 
 
Matrix3X3 scalarMultiply( Matrix3X3 a, float scale ) 
{ 
Matrix3X3 result; 
for(int i=0;i<3; i++) 
for(int j=0;j<3; j++) 
result.index[j][i] = scale * a.index[j][i] 
} 
Matrix3X3 subtractMatrices( Matrix3X3 a, Matrix3X3 b ) 
{ 
Matrix3X3 result; 
for(int i=0;i<3; i++) 
for(int j=0;j<3; j++) 
result.index[j][i] =a.index[j][i] - b.index[j][i]; 
} 

 
void printMatrix( Matrix3X3 a )
{
//loop through rows
for( int i=0; i < 3; ++i )
{
//loop through column at each row
for( int j=0; j < 3; ++j )
{
//i is the row
//j is the column
float temp = a.index[i][j];
cout << temp << " ";
}
//go to the next line after each row
cout << endl;
}
}
 
Matrix3X3 inputMatrix()
{
Matrix3X3 temp;
 
//loop through rows
for( int i=0; i < 3; ++i )
{
//loop through column at each row
for( int j=0; j < 3; ++j )
{
//i is the row
//j is the column
cout << "Enter row " << i << " column " << j << ":" << endl;
cin >> temp.index[i][j];
}
}
 
return temp;
}

Last edited by WaltP : Dec 13th, 2006 at 1:49 am. Reason: You've been asked to use code tags more than once.

•

Join Date: Jul 2005

Posts: 1,157

Reputation: Lerner is just really nice

Rep Power: 9

Solved Threads: 152

Lerner

Offline

Veteran Poster

Re: Homework assistance

Dec 12th, 2006

And there's some animal screaming bloody murder out my window at the moment too, but without anymore information about the problem I'm just as helpless in either case. Please indicate what the problem is, not just that you have one.

Also, please enclose your code in code tags---read the FAQ at the top of the board if you don't know how to do so.

•

Join Date: Apr 2006

Location: Canada

Posts: 4,504

Reputation: John A is a glorious beacon of light

Rep Power: 17

Solved Threads: 275

John A

Online

Vampirical Moderator

Re: Homework assistance

Dec 12th, 2006

Shall I go through with the standard procedure?

Don't use void main. It's bad for you. (Or rather, for your OS)

Did you forget a << endl; at the end of your statement? (Also missing closing brace)

Help with Code Tags

(Toggle Plain Text)

cout << "Please enter matrix B:" << endl;

Matrix3X3 B = inputMatrix () ;

cout << "Matrix B:" <

printMatrix ( B );
// missing closing }

Missing semicolon:

Help with Code Tags

(Toggle Plain Text)

Matrix3X3 scalarMultiply( Matrix3X3 a, float scale )
{
Matrix3X3 result;
for(int i=0;i<3; i++)
for(int j=0;j<3; j++)
result.index[j][i] = scale * a.index[j][i] // add ;

Try that, and your code should compile.

tuxation.com - Linux articles, tutorials, and discussions

•

Join Date: May 2006

Location: Bellevue, WA

Posts: 1,548

Reputation: Infarction has a spectacular aura about

Rep Power: 8

Solved Threads: 51

Infarction Infarction is offline

Offline

Battle Programmer

Re: Homework assistance

Dec 12th, 2006

are scalarMultiply and subractMatrices returning anything?

•

Join Date: Apr 2006

Location: Canada

Posts: 4,504

Reputation: John A is a glorious beacon of light

Rep Power: 17

Solved Threads: 275

John A

Online

Vampirical Moderator

Re: Homework assistance

Dec 12th, 2006

•

Originally Posted by Infarction

are scalarMultiply and subractMatrices returning anything?

Good point. :cheesy: Another function that has a similar state to the other 2 is inputMatrix.

tuxation.com - Linux articles, tutorials, and discussions

•

Join Date: Nov 2006

Posts: 6

Reputation: solomon grundy is an unknown quantity at this point

Rep Power: 0

Solved Threads: 0

solomon grundy solomon grundy is offline

Offline

Newbie Poster

Re: Homework assistance

Dec 13th, 2006

No it's not, and thats the problem, After I Build it and run it. It will input matrix A and then tell me to input Matrix B, after I put in numbers to Matrix B however after that its done. What am I missing?