Arduino sketches are written in C++.

Here is a typical construct you&#39;ll encounter:

    LiquidCrystal lcd(12, 11, 5, 4, 3, 2);
    ...
    lcd.begin(16, 2);
    lcd.print(&quot;Hello, World!&quot;);

That&#39;s C++, not C.

Both are supported. To quote the [Arduino homepage](http://code.google.com/p/arduino/),

&gt; The core libraries are written in C and C++ and compiled using avr-gcc

Note that C++ is a superset of C (well, [almost](http://www.stroustrup.com/bs_faq.html#C-is-subset)), and thus can often look very similar. I am not an expert, but I guess that most of what you will program for the Arduino in your first year on that platform will not need anything but plain C.


I want to start using Twitter&#39;s Bootstrap for a recently started Django app. I have quite a bit of experience with Django, but I&#39;m totally new to Bootstrap.

What&#39;s the best way to proceed? Are there any particular Boostrap apps for Django you would recommend or have experience with?

I understand that I could use Bootstrap directly, without any special Bootstrap-specific Django apps. However, I also read that the form rendering doesn&#39;t come out particularly well without a little server side support (rendering the Bootstrap specific CSS into the form HTML, for example).

There seem to be several projects, such as crispy forms, django-bootstrap-toolkit, etc. Looking at their project pages, I can see different levels of activity and support. If I decide to go with one of those, I would of course like to pick one which has some momentum and therefore a good likelihood of staying supported and maintained for a while. This is very important and so even if the particular app doesn&#39;t have all possible features or is a bit less flexible, it might still be a good choice, due to support/freshness, availability of examples, etc.

Thank you for any recommendations or feedback.


Django and Bootstrap: What app is recommended?

I want to add a space to some output after every 4th character until the end of the string.
I tried:

    $str = $rows[&#39;value&#39;];
    &lt;? echo substr($str, 0, 4) . &#39; &#39; . substr($str, 4); ?&gt;

Which just got me the space after the first 4 characters.

How can I make it show after every 4th ?

Add space after every 4th character

I see in one place that Arduino uses &#39;standard&#39; C, and in another that it uses &#39;standard&#39; C++, so on and so forth.

Which is it?

Does Arduino use C or C++?

<p>I see in one place that Arduino uses 'standard' C, and in another that it uses 'standard' C++, so on and so forth.</p>
<p>Which is it?</p>


Consider a type T supporting the default move semantics. Also consider the function below:

    T f() {
       T t;
       return t;
    }
    
    T o = f();

In the old C++03, some non-optimal compilers might call the copy constructor twice, one for the &quot;return object&quot; and one for `o`.

In c++11, since `t` inside `f()` is an lvalue, those compilers might call the copy constructor one time as before, and then call the move constructor for o.

Is it correct to state that the only way to avoid the first &quot;extra copy&quot; is to move `t` when  returning?

    T f() {
       T t;
       return std::move(t);
    }



Using std::move() when returning a value from a function to avoid to copy

Is there a way to create an ostream instance which basically doesn&#39;t do anything ?

For example :

    std::ostream dummyStream(...);
    dummyStream &lt;&lt; &quot;Nothing will be printed&quot;;

I could just create an ostringstream, but data will be buffered (and I really don&#39;t want to make anything with them, so it adds a useless overhead).

Any idea ?

**[edit]** Found this [related question](https://stackoverflow.com/questions/8243743/is-there-a-null-stdostream-implementation-in-c-or-libraries) which suits my needs. However, I think it could be useful to have a answer saying how to create a *valid* (no badbit) output stream with standard c++.

Standard no-op output stream

I have a couple of small questions. 

Firstly is there a difference between multithreading and multicore? Are they two completely different things or does multithreading use more than one core if it needs? 

Secondly Most cores have two threads but when profiling my app I noticed lots of different threads ranging from thread 128 to thread 3460. What dictates how many threads your computer has?

Thanks

Multithreading and multicore differences

This may just be a simple mistake that I&#39;m not seeing, but 
I think I&#39;m simply doing something wrong. Don&#39;t worry I&#39;m not using namespace std in my header
 functions or anything which seemed to be this person&#39;s issue [Question I read similar to 
mine][1] [1]: https://stackoverflow.com/questions/5527665/weird-string-does-not-name-a-type-

I am getting 4 errors right now:

&gt;  C:\Documents and Settings\Me\My
&gt; Documents\C++Projects\C++\RandomSentence\Nouns.h|8|error: &#39;string&#39; in
&gt; namespace &#39;std&#39; does not name a type|
&gt; 
&gt; C:\Documents and Settings\Me\My
&gt; Documents\C++Projects\C++\RandomSentence\Nouns.h|12|error: &#39;string&#39; in
&gt; namespace &#39;std&#39; does not name a type|
&gt; 
&gt; C:\Documents and Settings\Me\My
&gt; Documents\C++Projects\C++\RandomSentence\Nouns.h|13|error: &#39;string&#39; in
&gt; namespace &#39;std&#39; does not name a type|
&gt; 
&gt; C:\Documents and Settings\Me\My
&gt; Documents\C++Projects\C++\RandomSentence\Nouns.cpp|9|error: no
&gt; &#39;std::string Nouns::nounGenerator()&#39; member function declared in class
&gt; &#39;Nouns&#39;|
&gt; 
&gt; ||=== Build finished: 4 errors, 0 warnings ===|

Here is my header file:

    class Nouns
    {
        public:
            Nouns();
            std::string noun;
        protected:
        private:
            int rnp; // random noun picker
            std::string dog, cat, rat, coat, toilet, lizard, mime, clown, barbie, pig, lamp, chair, hanger, pancake, biscut, ferret, blanket, tree, door, radio;
            std::string nounGenerator()
    };

And this is my cpp file:
  

    #include &quot;Nouns.h&quot;
    #include &lt;iostream&gt;
    
    Nouns::Nouns()
    {
    
    }
    
    std::string Nouns::nounGenerator(){
        RollRandom rollRandObj;
    
        rnp = rollRandObj.randNum;
    
        switch(rnp){
        case 1:
            noun = &quot;dog&quot;;
            break;
        case 2:
            noun = &quot;cat&quot;;
            break;
        case 3:
            noun = &quot;rat&quot;;
            break;
        case 4:
            noun = &quot;coat&quot;;
            break;
        case 5:
            noun = &quot;toilet&quot;;
            break;
        case 6:
            noun = &quot;lizard&quot;;
            break;
        case 7:
            noun = &quot;mime&quot;;
            break;
        case 8:
            noun = &quot;clown&quot;;
            break;
        case 9:
            noun = &quot;barbie&quot;;
            break;
        case 10:
            noun = &quot;pig&quot;;
            break;
        case 11:
            noun = &quot;lamp&quot;;
            break;
        case 12:
            noun = &quot;chair&quot;;
            break;
        case 13:
            noun = &quot;hanger&quot;;
            break;
        case 14:
            noun = &quot;pancake&quot;;
            break;
        case 15:
            noun = &quot;biscut&quot;;
            break;
        case 16:
            noun = &quot;ferret&quot;;
            break;
        case 17:
            noun = &quot;blanket&quot;;
            break;
        case 18:
            noun = &quot;tree&quot;;
            break;
        case 19:
            noun = &quot;door&quot;;
            break;
        case 20:
            noun = &quot;radio&quot;;
            break;
        }
    
        return noun;
    }

string in namespace std does not name a type

In the code below, I define a trivial `log` function. In `main` I try *not* to call it; I call `std::log`. Nevertheless, my own `log` is called; and I see &quot;log!&quot; on screen. Does anyone know why? I use G++ 4.7 and clang++ 3.2.

    #include &lt;iostream&gt;
    #include &lt;cmath&gt;
    
    double log(const double x) { std::cout &lt;&lt; &quot;log!\n&quot;; return x; }
    
    int main(int argc, char *argv[])
    {
      std::log(3.14);
      return 0;
    }



Why is my log in the std namespace?

I am trying to compile a program which uses [udis86][1] library. Actually I am using an example program given in the [user-manual][2] of the library. But while compiling, it gives error. The errors I get are: 

    example.c:(.text+0x7): undefined reference to &#39;ud_init&#39;
    example.c:(.text+0x7): undefined reference to &#39;ud_set_input_file&#39;
    .
    .
    example.c:(.text+0x7): undefined reference to &#39;ud_insn_asm&#39;


The command I am using is:

    $ gcc -ludis86 example.c -o example 
as instructed in the user-manual.

Clearly, linker is not able to link libudis library. But if I change my command to:

    $ gcc example.c -ludis86 -o example 
It starts working. So can please someone explain what is the problem with the first command? 

  [1]: http://udis86.sourceforge.net/
  [2]: http://udis86.sourceforge.net/manual/manual.html#id486176

Why does the order of &#39;-l&#39; option in gcc matter?

If I have:

	unsigned int x;
	x -= x;

it&#39;s clear that `x` *should* be zero after this expression, but everywhere I look, they say the *behavior* of this code is undefined, not merely the value of `x` (until before the subtraction).

Two questions:

- Is the *behavior* of this code indeed undefined?  
  (E.g. Might the code crash [or worse] on a compliant system?)

- If so, ***why*** does C say that the *behavior* is undefined, when it is perfectly clear that `x` should be zero here?

	i.e. What is the *advantage* given by not defining the behavior here?  

Clearly, the compiler could simply use *whatever* garbage value it deemed &quot;handy&quot; inside the variable, and it would work as intended... what&#39;s wrong with that approach?

(Why) is using an uninitialized variable undefined behavior?

I am trying to print the results of an MD5 hash to the console and it is working for the most part. To ensure correctness, I used an online MD5 calculator to compare results. Most of the characters are the same, but a few are missing in mine and they are are all leading zeroes.

Let me explain. The result is a 16 byte unsigned char *. I print each of these bytes one by one. Each byte prints TWO characters to the screen. However, if the first character out of the two is a zero, it does not print the zero. 

    printk(&quot;%x&quot;, result);

Result is of type unsigned char*. Am I formatting it properly or am I missing something?

Printing leading zeroes for hexadecimal in C

I am trying to control Dynamixel servos using a GUI made using Qt. Dynamixel provides a C set of [C libraries][1] to control the motors, while the only way of making GUI&#39;s I know is Qt, which is essentially C++. Will it be possible to use Dynamixel C libraries from Qt C++ code in any way?


  [1]: http://support.robotis.com/en/software/dynamixel_sdk/api_reference.htm

Using C Libraries for C++ Programs

Is typeof in C, really an operator?  
I&#39;m thinking because there is no polymorphism in C, that there is nothing to do at run-time.  That is, the answer to typeof is known at compile-time.  (I can&#39;t think of a use of typeof that would not be known at compile time.) So it appears to be more of a compile-time directive, than an operator.  

Does typeof use any (processor) run-time (in GCC)?

typeof operator in C

How can I use [C++11][1] when programming the Arduino?

I would be fine using either the Arduino IDE or another environment. I am most interested in the core language improvements, not things that require standard library changes.

  [1]: https://en.wikipedia.org/wiki/C%2B%2B11







How can I use a C++11 to program the Arduino?

In the Arduino GUI on windows, if I click on Sketch --&gt; Import Library, at the bottom of the menu there is a section called &quot;Contributed&quot;.

Unfortunately, I had misclicked and added a library I did not want to that list.

**How can I remove it from that list?**

The help page only mentions that &quot;If a sketch no longer needs a library, simply delete its #include statements from the top of your code&quot; but it does not mention how to remove the library from the list of contributed libraries.

How do I remove a library from the arduino environment?

I am running Debian 7 (Linux Crunchbang) and wanted to use The Arduino IDE to program my Arduino UNO. To do that I installed the package `arduino`. When I started the Arduino I was asked to add my user to the `dialout` group. So I did with `sudo usermod -a -G dialout &lt;my-username&gt;`. 

However when I start the Arduino IDE using `arduino` in the commandline the IDE opens but I am not able to load my program to the Arduino. The  error message is &quot;Serial port COM1 not found. Did you select the right one from the Tools &gt; Serial Port menu?&quot; And when I went to select the Serial Port, the option &quot;Tools &gt; Serial Port&quot; is greyed out. 

I thought it is because I did not grant read and write permissions on my usb port (ttyACM0). So I did `sudo chmod a+rw /dev/ttyACM0` but the option is still greyed out.

Arduino Tools &gt; Serial Port greyed out

I have an Arduino Duemilanove with an [ATmega328][1]. I am working on [Ubuntu&amp;nbsp;12.04][2] (Precise Pangolin), and the Arduino IDE&#39;s version is 1.0. Recently, I tried to upload a few of the sample sketches onto it, such as the Blink one. However, none of my attempts are working and they result in the same error every time I try it:

&gt; avrdude: stk500_recv(): programmer is not responding.

[![][3]][3]

I have enabled `/dev/ttyUSB0` under menu *Tools* &amp;rarr; *Serial Port*. I have also selected the correct board (Duemilanove with ATmega328) from the list. Yet, I am not able to resolve the issue. I have searched online as well and none of the other responses for this problem seem to be working for me. Why I am encountering this issue and how to resolve it?

I also tried turning the onboard ATmega and fitting it in the other direction. Now, I encounter no problems uploading, but nothing happens afterwards. The onboard LED also does not seem to be blinking.

  [1]: https://en.wikipedia.org/wiki/ATmega328
  [2]: https://en.wikipedia.org/wiki/Ubuntu_version_history#Ubuntu_12.04_LTS_.28Precise_Pangolin.29
  [3]: http://i.stack.imgur.com/0AdVe.png



Arduino Sketch upload issue - avrdude: stk500_recv(): programmer is not responding

I&#39;m currently working on a project where I need to use an Arduino Nano (http://arduino.cc/en/Main/arduinoBoardNano) to send data from a temperature sensor to a web server.

At first I thought it would be easy, since there are so many great libraries out there to help with POST/GET etc. However, my professor just told me that I need to send data to the server using TCP/IP, and as I understand it POST and GET are HTTP methods.

Could someone explain to me the difference between HTTP and TCP/IP? Specifically as it relates to sending data to a web server. I&#39;m looking for an answer that isn&#39;t too technical (I&#39;m pretty new to all of this).

Finally, if there is anyone out there with experience making an Arduino do what I&#39;ve described above, I would really appreciate some pointers.

Thanks!

Content Type	Original Author	Original Content on Stackoverflow
Question	memilanuk	View Question on Stackoverflow
Solution 1 - C++	user1157391	View Answer on Stackoverflow
Solution 2 - C++	tiwo	View Answer on Stackoverflow

Does Arduino use C or C++?

C++ Problem Overview

C++ Solutions

Solution 1 - C++

Solution 2 - C++

Add space after every 4th character

Django and Bootstrap: What app is recommended?

Attributions