C / C++ / MFC

4-Feb-14 16:50

I would like to output three columns of numbers with the decimal points lined up. I wrote the following piece of code which I thought would do it.

C++

for( int i = 0; i<100; i++ ) {
    double f1 = (int)(i/20);
    double f2 = 3.1415*i;
    double f3 = 3.1415*(f2+3);
    cout.width( 10 );
    cout.precision( 4 );
    cout << std::left << f1 << " ";
    cout.width( 10 );
    cout << std::left << f2 << " ";
    cout.width( 10 );
    cout << std::left << f3 << endl;
}

However, the decimal points are not lined up. Also, I want to do this in C++ not C. That is, I do not want to use, printf, fprintf or sprintf. How do I get the decimal points to line up vertical?

Thanks
Bob

Malli_S4-Feb-14 21:58

Malli_S

4-Feb-14 21:58

Check if this is helpful.

{
		cout << fixed;
		for( int i = 0; i<10; i++ ) {
			double f1 = (int)(i/20);
			double f2 = 3.1415*i;
			double f3 = 3.1415*(f2+3);
			std::cout << std::setfill (' ') << std::setw (10);
			cout.width( 10 );
			cout.precision( 4 );
			cout << f1 << " ";
			cout.width( 10 );
			cout << f2 << " ";
			cout.width( 10 );
			cout << f3 << endl;
		}

		getch();
	}

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-Malli...!

BobInNJ5-Feb-14 3:24

5-Feb-14 3:24

Thanks for the response. However, it failed to produce the results I wanted. Here is part of the output that I got:

0          0      9.425
0      3.142      19.29
0      6.283      29.16
0      9.425      39.03
0      12.57       48.9
0      15.71      58.77

The decimal points are not lined up. What I want is:

0      0.0         9.425
0      3.142      19.29
0      6.283      29.16
0      9.425      39.03
0     12.57       48.9
0     15.71       58.77

In what I want the decimal points are all in the same column.

Malli_S5-Feb-14 21:12

Malli_S

5-Feb-14 21:12

But at my end I'm getting proper output.

Have a look at this[^].

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David Crow5-Feb-14 6:18

David Crow

5-Feb-14 6:18

Have you tried removing std::left?

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BobInNJ5-Feb-14 11:10

5-Feb-14 11:10

I tried it with std::left, without std::left and with std::right. In all three cases it did not work. What I believe the problem is that there is no way to specified a fixed number of digits along with a fixed number of digits to the right of the decimal point. I think I am going to go use sprintf and then send the output the string sprintf produces. It is not the "C++ way" of doing things but it works.

I want to thank the group for their responses.

Bob

David Crow5-Feb-14 16:07

David Crow

5-Feb-14 16:07

Try adding cout << setiosflags(ios::fixed) right before the for() loop.

BobInNJ6-Feb-14 2:10

Proper array memory management in C++

6-Feb-14 2:10

David,

Adding the line:

C++

cout << setiosflags(ios::fixed);

before the for loop did the trick. The program now works as expected. I am
happy.

I thank you and all the other people who responded to my post for their help in this matter.

Bob

Don Guy3-Feb-14 12:43

Don Guy

3-Feb-14 12:43

I have an application that randomly displays images on a screen. There's a capture button, and when user clicks on that button, the image that is currently displayed is stored into a buffer.
User can click the button 5 times. i.e., the buffer should be storing upto 5 image data.

I have code like this,

.h File:

unsigned char* m_ImageBuffer[5];

.cpp File:

while (1)
{
----------
----------
m_ImageBuffer[counter] = new unsigned char[size];
memcpy(m_ImageBuffer[counter], pImageData, size);
----------
----------
}

The variable "counter" goes from 0 to 4. Inside the WHILE loop a bunch of images are constantly displayed
in the screen.

The purpose of m_ImageBuffer is that, i will store the user selected image data in this buffer, so that it could be later used for display. i.e., in a different screen.

The problem with the code in WHILE loop is that, i am not able to use DELETE properly. So the code logic basically ends up eating so much memory.

I am looking for a better logic, by which i can store the image data, but still does better memory management.

Not sure the problem is explained properly. I am expecting some suggestions on how to manage this situation.

Thanks in advance.

Richard MacCutchan3-Feb-14 21:42

Richard MacCutchan

3-Feb-14 21:42

At the beginning of the program initialise the buffer so all pointers are NULL. Then every time you save an image, check if the pointer is not null and if so delete[] it. Something like:

C++

if (m_ImageBuffer[counter] != NULL)
    delete[] m_ImageBuffer[counter];
m_ImageBuffer[counter] = new unsigned char[size];
memcpy(m_ImageBuffer[counter], pImageData, size);

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Maximilien4-Feb-14 5:26

Maximilien

4-Feb-14 5:26

Proper c++ memory management would tell you to use standard c++ classes and collections instead of arrays and pointers to data.

Change the array to either a std::vector or a std::array (if c++11).

If possible I would replace the unsigned char* with a proper image class (if on Windows, CImage, CBitmap, ... )

If you need something portable and want to keep the unsigned char* , create a wrapper class around it with proper constructor/destructor/copy/assignment methods.

I'd rather be phishing!

jschell6-Feb-14 8:34

jschell

6-Feb-14 8:34

Maximilien wrote:
Proper c++ memory management would tell you to use standard c++ classes and collections...

None those suggestions however would fix the problem of increasing memory usage. Where the first response does.