Because typical floating point formats don&#39;t support unsigned numbers. See, for instance, [this list of IEEE 754 formats][1].

Adding a numerical format that isn&#39;t supported by common hardware just makes life difficult for compiler writers, and is probably not considered worth the effort.


  [1]: http://en.wikipedia.org/wiki/IEEE_754-2008#Formats

C++ doesn&#39;t support unsigned floating point types because most floating point hardware doesn&#39;t support unsigned floating point types. Some graphics cards do work with unsigned floating point, but it&#39;s generally internal, not really visible to a program or user.

Unsigned integers gain an extra bit of precision and have slightly different bit-wise semantics to signed integers. Floats and doubles always reserve a bit for the sign (on most hardware) and have no bit-wise semantics, so there&#39;s no real benefit in having an unsigned real type.

So I know its a fairly big challenge but I want to write a basic movie player/converter in c# using the FFmpeg library. However, the first obstacle I need to overcome is wrapping the FFmpeg library in c#. I&#39;ve downloaded ffmpeg but couldn&#39;t compile it on Windows, so I downloaded a precompiled version for me. Ok awesome. Then I started looking for C# wrappers.

I have looked around and have found a few wrappers such as SharpFFmpeg (http://sourceforge.net/projects/sharpffmpeg/) and ffmpeg-sharp (http://code.google.com/p/ffmpeg-sharp/). First of all, I wanted to use ffmpeg-sharp as its LGPL and SharpFFmpeg is GPL. However, it had quite a few compile errors. Turns out it was written for the mono compiler, I tried compiling it with mono but couldn&#39;t figure out how. I then started to manually fix the compiler errors myself, but came across a few scary ones and thought I&#39;d better leave those alone. So I gave up on ffmpeg-sharp.

Then I looked at SharpFFmpeg and it looks like what I want, all the functions P/Invoked for me. However its GPL? Both the AVCodec.cs and AVFormat.cs files look like ports of avcodec.c and avformat.c which I reckon I could port myself? Then not have to worry about licencing.

But I want to get this right before I go ahead and start coding. Should I:

1. Write my own C++ library for interacting with ffmpeg, then have my C# program talk to the C++ library in order to play/convert videos etc.

OR

2. Port avcodec.h and avformat.h (is that all i need?) to c# by using a whole lot of DllImports and write it entirely in C#?

First of all consider that I&#39;m not great at C++ as I rarely use it but I know enough to get around. The reason I&#39;m thinking #1 might be the better option is that most FFmpeg tutorials are in C++ and I&#39;d also have more control over memory management than if I was to do it in c#.

What do you think?
Also would you happen to have any useful links (perhaps a tutorial) for using FFmpeg?

Using FFmpeg in .net?

I have a dialog that I show with `&lt;class&gt;.ShowDialog()`. It has an OK button and a Cancel button; the OK button also has an event handler.

I want to do some input validation in the event handler and, if it fails, notify the user with a message box and prevent the dialog from closing. I don&#39;t know how to do the last part (preventing the close).

Preventing a dialog from closing in the button&#39;s click event handler

Why doesn&#39;t C++ support unsigned double syntax?

Unsigned double in C++?

<p>Why doesn't C++ support unsigned double syntax?</p>


I have the following code inside the .h file and I&#39;m not sure what does the assignment statement do and how is it called properly?

    virtual void yield() = 0;

I thought that the function returns a value of 0 by default but since this function returns void I am a little bit confused. Can anyone comment on this and maybe say how can I refer to this assignment, I mean how is it called in C++ jargon?

Thanks.

C++ header file and function declaration ending in &quot;= 0&quot;

I was trying to convert a QString to char* type by the following methods, but they don&#39;t seem to work.

    //QLineEdit *line=new QLineEdit();{just to describe what is line here}

    QString temp=line-&gt;text();
    char *str=(char *)malloc(10);
    QByteArray ba=temp.toLatin1();
    strcpy(str,ba.data());

Can you elaborate the possible flaw with this method, or give an alternative method?

QString to char* conversion

In the `stdint.h` (C99), [boost/cstdint.hpp](http://www.boost.org/doc/libs/1_42_0/libs/integer/doc/html/boost_integer/cstdint.html), and `cstdint` (C++0x) headers there is, among others, the type `int32_t`.

Are there similar fixed-size floating point types? Something like `float32_t`?

Fixed-size floating point types

Lately, I&#39;ve been trying to learn C++ from [this website][1]. Unfortunately whenever I try to run one of the code samples, I see that program open for about a half second and then immediately close. Is there a way to stop the program from closing immediately so that I can see the fruits of my effort?

  [1]: http://www.cplusplus.com/doc/tutorial/


How to stop C++ console application from exiting immediately?

I was given the following as an interview question:

    class A
    {
    public:
        void fun()
        {
            std::cout &lt;&lt; &quot;fun&quot; &lt;&lt; std::endl;
        }
    };
    
    A* a = NULL;
    a-&gt;fun();

What will happen when this code is executed, and why?

---

### See also: 
* [When does invoking a member function on a null instance result in undefined behavior?](https://stackoverflow.com/questions/2474018/when-does-invoking-a-member-function-on-a-null-instance-result-in-undefined-behav)

What will happen when I call a member function on a NULL object pointer?

Right now I&#39;m trying this: 

    int a = round(n);

where `n` is a `double` but it&#39;s not working. What am I doing wrong? 


Rounding a double to turn it into an int (java)

If the value is `200.3456`, it should be formatted to `200.34`.
If it is `200`, then it should be `200.00`.

Round a double to 2 decimal places

For converting a byte array to a double I found this:

    //convert 8 byte array to double
    int start=0;//???
    int i = 0;
		int len = 8;
		int cnt = 0;
		byte[] tmp = new byte[len];
		for (i = start; i &lt; (start + len); i++) {
			tmp[cnt] = arr[i];
			//System.out.println(java.lang.Byte.toString(arr[i]) + &quot; &quot; + i);
			cnt++;
		}
		long accum = 0;
		i = 0;
		for ( int shiftBy = 0; shiftBy &lt; 64; shiftBy += 8 ) {
			accum |= ( (long)( tmp[i] &amp; 0xff ) ) &lt;&lt; shiftBy;
			i++;
		}
		
            return Double.longBitsToDouble(accum);


But I could not find anything which would convert a double into a byte array.

How can I convert a byte array into a double and back?

This is something that&#39;s been on my mind for years, but I never took the time to ask before.

Many (pseudo) random number generators generate a random number between 0.0 and 1.0. Mathematically there are infinite numbers in this range, but `double` is a floating point number, and therefore has a finite precision.

So the questions are:

1. Just how many `double` numbers are there between 0.0 and 1.0?
2. Are there just as many numbers between 1 and 2? Between 100 and 101? Between 10^100 and 10^100+1?

Note: if it makes a difference, I&#39;m interested in Java&#39;s definition of `double` in particular.

How many double numbers are there between 0.0 and 1.0?

I would like to change decimal point to another character in C#. I have a `double` variable `value`

    double value;

and when I use the command:

    Console.WriteLine(value.ToString()); // output is 1,25

I know I can do this:

    Console.WriteLine(value.ToString(
        CultureInfo.CreateSpecificCulture(&quot;en-GB&quot;))); // output is 1.25

but I don&#39;t like it very much because it&#39;s very long and I need it quite often in my program.

Is there a shorter version for setting &quot;decimal point&quot; really as point and not comma as is in my culture is usual?

How to change symbol for decimal point in double.ToString()?

I was curious to know what would happen if I assign a negative value to an unsigned variable.

The code will look somewhat like this.

    unsigned int nVal = 0;
    nVal = -5;

It didn&#39;t give me any compiler error. When I ran the program the `nVal` was assigned a strange value! Could it be that some 2&#39;s complement value gets assigned to `nVal`?




What happens if I assign a negative value to an unsigned variable?

I can never understand how to print `unsigned long` datatype in C.

Suppose `unsigned_foo` is an `unsigned long`, then I try:

* `printf(&quot;%lu\n&quot;, unsigned_foo)`
* `printf(&quot;%du\n&quot;, unsigned_foo)`
* `printf(&quot;%ud\n&quot;, unsigned_foo)`
* `printf(&quot;%ll\n&quot;, unsigned_foo)`
* `printf(&quot;%ld\n&quot;, unsigned_foo)`
* `printf(&quot;%dl\n&quot;, unsigned_foo)`

And all of them print some kind of `-123123123` number instead of `unsigned long` that I have.

How to printf &quot;unsigned long&quot; in C?

I know about `int` and `long` (32-bit and 64-bit numbers), but what are `uint` and `ulong`?

What is the difference between “int” and “uint” / “long” and “ulong”?

I am trying to convert a signed byte in unsigned. The problem is the data I am receiving is unsigned and Java does not support unsigned byte, so when it reads the data it treats it as signed.

I tried it to convert it by the following solution I got from Stack&amp;nbsp;Overflow.

    public static int unsignedToBytes(byte a)
    {
        int b = a &amp; 0xFF;
        return b;
    }

But when again it&#39;s converted in byte, I get the same signed data. I am trying to use this data as a parameter to a function of Java that accepts only a byte as parameter, so I can&#39;t use any other data type. How can I fix this problem?


Can we make unsigned byte in Java

So I know that the difference between a `signed int` and `unsigned int` is that a bit is used to signify if the number if positive or negative, but how does this apply to a `char`? How can a character be positive or negative?

Content Type	Original Author	Original Content on Stackoverflow
Question	lost3den	View Question on Stackoverflow
Solution 1 - C++	unwind	View Answer on Stackoverflow
Solution 2 - C++	Jerry Coffin	View Answer on Stackoverflow
Solution 3 - C++	Marcelo Cantos	View Answer on Stackoverflow

Unsigned double in C++?

C++ Problem Overview

C++ Solutions

Solution 1 - C++

Solution 2 - C++

Solution 3 - C++

Preventing a dialog from closing in the button's click event handler

Using FFmpeg in .net?

Attributions