Ad:

C++ Discussion Thread
Unsolved
Views: 1360

Dec 11th, 2006

Homework assistance

Expand Post »

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

C++ 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 3:06 pm. Reason: Added code tags learn to use them yourself.

Similar Threads

solomon grundy

Reputation Points: 10

Solved Threads: 0

Newbie Poster

Offline

6 posts
since Nov 2006

Permalink

Dec 11th, 2006

Re: Homework assistance

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 2:58 pm.

Infarction

Reputation Points: 683

Solved Threads: 53

Posting Virtuoso

Offline

1,580 posts
since May 2006

Permalink

Dec 12th, 2006

Re: Homework assistance

I'm still having trouble making this code work

(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 2:49 am. Reason: You've been asked to use code tags more than once.

solomon grundy

Reputation Points: 10

Solved Threads: 0

Newbie Poster

Offline

6 posts
since Nov 2006

Permalink

Dec 12th, 2006

Re: Homework assistance

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.

Lerner

Reputation Points: 718

Solved Threads: 373

Nearly a Posting Maven

Offline

2,253 posts
since Jul 2005

Permalink

Dec 12th, 2006

Re: Homework assistance

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)

(Toggle Plain Text)

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

Matrix3X3 B = inputMatrix () ;

cout << "Matrix B:" <

printMatrix ( B );
// missing closing }

Missing semicolon:

(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.

John A

Team Colleague

Reputation Points: 2240

Solved Threads: 338

Vampirical Lurker

Offline

5,055 posts
since Apr 2006

Permalink

Dec 12th, 2006

Re: Homework assistance

are scalarMultiply and subractMatrices returning anything?

Infarction

Reputation Points: 683

Solved Threads: 53

Posting Virtuoso

Offline

1,580 posts
since May 2006

Permalink

Dec 12th, 2006

Re: Homework assistance

Click to Expand / Collapse Quote 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.

John A

Team Colleague

Reputation Points: 2240

Solved Threads: 338

Vampirical Lurker

Offline

5,055 posts
since Apr 2006

Permalink

Dec 13th, 2006

Re: Homework assistance

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?

solomon grundy

Reputation Points: 10

Solved Threads: 0

Newbie Poster

Offline

6 posts
since Nov 2006

Permalink

Dec 13th, 2006

Re: Homework assistance

how about return result;?

Infarction

Reputation Points: 683

Solved Threads: 53

Posting Virtuoso

Offline

1,580 posts
since May 2006

This thread is more than three months old

No one has posted to this discussion for at least three months. Please let old threads die and do not reply to them unless you feel you have something new and valuable to contribute that absolutely must be added to make the discussion complete. Otherwise, please start a new thread in this forum instead.

Previous Thread in C++ Forum Timeline: Still need help with opening a file and store the data on it in an array

Next Thread in C++ Forum Timeline: I am having some issues with some basic .net c++

DaniWeb Message

Cancel Changes

User Name
Password