`false == 0` and `true = !false`. I.e. anything that is not zero and can be converted to a boolean is not `false`, thus it _must_ be `true`. Some examples to clarify:

    if(0)          // false
    if(1)          // true
    if(2)          // true

    if(0 == false) // true
    if(0 == true)  // false

    if(1 == false) // false
    if(1 == true)  // true

    if(2 == false) // false
    if(2 == true)  // false

    cout &lt;&lt; false  // 0
    cout &lt;&lt; true   // 1

`true` is equal to `1`, but any  non-zero `int` _evaluates_ to `true` but is not _equal_ to `true` except `1`.

Yes that is correct.  &quot;Boolean variables only have two possible values: true (1) and false (0).&quot;
[cpp tutorial on boolean values][1]


  [1]: http://www.learncpp.com/cpp-tutorial/26-boolean-values/

I&#39;m using the the C++/Qt print function qDebug, 
but sometimes I would like to control how &quot;, space and newline is appended 
and not use the default qDebug.

Let&#39;s take a simple example:

    QString var1(&quot;some string&quot;);
    int var2 = 1;
    qDebug() &lt;&lt; var1 &lt;&lt; &quot;=&quot; &lt;&lt; var2;

This will print 

    &quot;some string&quot; = 1 

But Let&#39;s say that I don&#39;t like the appended &quot; and space 
and would like the print to look like

    some string=1 

How to I then call qDebug?

---

Note: There is a function in [qDebug called nospace][1], but it will remove the spaces.
But the &quot; is still there.

If I use this:

    qDebug().nospace() &lt;&lt; var1 &lt;&lt; &quot;=&quot; &lt;&lt; var2;

I get:

    &quot;some string&quot;=1

But please note that I have still not found a way to get rid of the ending newline.

/Thanks

  [1]: http://doc.qt.io/qt-4.8/qdebug.html#nospace

How to call qDebug without the appended spaces and newline?

Hi I have files called MyCode.h and MyCode.cpp

In MyCode.h I have declared

    enum MyEnum {Something = 0, SomethingElse = 1};
    
    class MyClass {
    
    MyEnum enumInstance;
    void Foo();
    
    }; 

Then in MyCode.cpp:

    #include &quot;MyCode.h&quot;

    void MyClass::Foo() {
        enumInstance = MyEnum::SomethingElse;
    }


but when compiling with g++ I get the error &#39;MyEnum&#39; is not a class or namespace... 

(works fine in MS VS2010 but not linux g++)

Any ideas?
Thanks
Thomas

My enum is not a class or namespace

I was wondering, does `true` equal to 1 and `false` equal to 0 and how?

Does true equal to 1 and false equal to 0?

<p>I was wondering, does <code>true</code> equal to 1 and <code>false</code> equal to 0 and how?</p>


What is the difference between `char** argv` and `char* argv[]`? in `int main(int argc, char** argv)` and `int main(int argc, char* argv[])`?

Are they the same? Especially that the first part does not have `[]`.

C++ - char** argv vs. char* argv[]

I am using a library that defines output stream operators (operator&lt;&lt;) in the global namespace. In my own namespace, I was always declaring such operators in the global namespace, and never had problems with them. But now for various reasons I need to declare those operators in my own namespace, and suddenly, the compiler can&#39;t seem to find the operators declared in the library anymore.

Here&#39;s a simple example that illustrates my problem: 

    #include &lt;iostream&gt;
    
    namespace A
    {
       struct MyClass {};
    }
    
    std::ostream &amp; operator&lt;&lt;( std::ostream &amp; os, const A::MyClass &amp; )
       { os &lt;&lt; &quot;namespace A&quot;; return os; }
    
    namespace B
    {
       struct MyClass {};

       std::ostream &amp; operator&lt;&lt;( std::ostream &amp; os, const B::MyClass &amp; )
          { os &lt;&lt; &quot;namespace B&quot;; return os; }
    }

    namespace B
    {
       void Test()
       {
          std::cout &lt;&lt; A::MyClass() &lt;&lt; std::endl;
          std::cout &lt;&lt; B::MyClass() &lt;&lt; std::endl;
       }
    }
    
    int main()
    {
       B::Test();
       return 1;
    }

I am getting the following error:

    error: no match for ‘operator&lt;&lt;’ in ‘std::cout &lt;&lt; A::MyClass()’

Note that if both operators are within the namespaces, or alternatively if they are both in the global namespace, the code compiles and executes correctly.

I&#39;d really like to understand what&#39;s going on and also what the &quot;good practice&quot; for defining such operators with namespaces.

Thanks! 

Namespaces and operator resolution

I&#39;m trying to get a simple Java method call from C++ while Java calls native method. Here&#39;s the Java code:

    public class MainActivity extends Activity {
        private static String LIB_NAME = &quot;name&quot;;
    
        static {
            System.loadLibrary(LIB_NAME);
        }
    
        /** Called when the activity is first created. */
        @Override
        public void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.main);
            TextView tv = (TextView) findViewById(R.id.textview);
            tv.setText(this.getJniString());
        }
    
        public void messageMe(String text) {
            System.out.println(text);
        }
    
        public native String getJniString();
    }

I&#39;m trying to call `messageMe` method from native code in the process of `getJniString*` method call from Java to native.

native.cpp:

    #include &lt;string.h&gt;
    #include &lt;stdio.h&gt;
    #include &lt;jni.h&gt;
    
    jstring Java_the_package_MainActivity_getJniString( JNIEnv* env, jobject obj, jint depth ){
    
    //    JavaVM *vm;
    //    JNIEnv *env;
    //    JavaVMInitArgs vm_args;
    //    vm_args.version = JNI_VERSION_1_2;
    //    vm_args.nOptions = 0;
    //    vm_args.ignoreUnrecognized = 1;
    //
    //    // Construct a VM
    //    jint res = JNI_CreateJavaVM(&amp;vm, (void **)&amp;env, &amp;vm_args);
    
        // Construct a String
        jstring jstr = env-&gt;NewStringUTF(&quot;This string comes from JNI&quot;);
        // First get the class that contains the method you need to call
        jclass clazz = env-&gt;FindClass(&quot;the/package/MainActivity&quot;);
        // Get the method that you want to call
        jmethodID messageMe = env-&gt;GetMethodID(clazz, &quot;messageMe&quot;, &quot;(Ljava/lang/String;)V&quot;);
        // Call the method on the object
        jobject result = env-&gt;CallObjectMethod(jstr, messageMe);
        // Get a C-style string
        const char* str = env-&gt;GetStringUTFChars((jstring) result, NULL);
        printf(&quot;%s\n&quot;, str);
            // Clean up
        env-&gt;ReleaseStringUTFChars(jstr, str);
    
    //    // Shutdown the VM.
    //    vm-&gt;DestroyJavaVM();
    
        return env-&gt;NewStringUTF(&quot;Hello from JNI!&quot;);
    }


After clean compilation app stops with next message:

    ERROR/AndroidRuntime(742): FATAL EXCEPTION: main
            java.lang.NoSuchMethodError: messageMe
            at *.android.t3d.MainActivity.getJniString(Native Method)
            at *.android.t3d.MainActivity.onCreate(MainActivity.java:22)

Apparently it means that method name is wrong, but it looks OK to me. 


Calling a java method from c++ in Android

Someone brought [this article][1] to my attention that claims *(I&#39;m paraphrasing)* the STL term is misused to refer to the entire C++ Standard Library instead of the parts that were taken from SGI STL.

&gt; (...) it refers to the &quot;STL&quot;, despite the fact that very few people still use the STL (which was designed at SGI).
&gt;
&gt; Parts of the C++ Standard Library were based on parts of the STL, and it is these parts that many people (including several authors and the notoriously error-ridden cplusplus.com) still refer to as &quot;the STL&quot;. However, this is inaccurate; indeed, the C++ standard never mentions &quot;STL&quot;, and there are content differences between the two.
&gt;
&gt; (...) &quot;STL&quot; is rarely used to refer to the bits of the stdlib that happen to be based on the SGI STL. People think it&#39;s the entire standard library. It gets put on CVs. And it is misleading.

I hardly know anything about C++&#39;s history so I can&#39;t judge the article&#39;s correctness. Should I refrain from using the term STL? Or is this an isolated opinion?


  [1]: http://kera.name/articles/2010/08/it-is-not-called-the-stl-mmkay/

What&#39;s the difference between &quot;STL&quot; and &quot;C++ Standard Library&quot;?

Is there any way to convert C code to JavaScript and from JavaScript to C? I found `V8 juice` which can generate `JavaScript-side` classes from C++, but it&#39;s only one way (C++ to JavaScript).

I&#39;m not looking for a software.

Convert javascript code to c code

I realize that to become a better programmer, you need to program!
So obviously the more practice, the better you become. 

My problem is this. I am currently in university, and I find my course load is a bit daunting, and I don&#39;t have a lot of free time. I don&#39;t think I could really take on a big project, particularly I don&#39;t think I would have to motivation to see it through, it would be easier just for me to keep putting it off in favour of work that is due is school.

But I still want to practice. 
So I am looking for any resources which have programming challenges which can be completed in a fairly small amount of time. Ideally something i could get done in under 10 hours of work (so just over an hour of work each day), if not smaller. 

I have heard of Google Code Jam, but I am not sure the length of the programs it specifies, nor the skill level. 


Does anyone have suggestions? Even perhaps a compendium of tutorials for different functions might be useful. For example, a tutorial on file IO would be worthwhile (if I didn&#39;t already know it), even though it can be a fairly small topic.

Very small programs to improve programming skills?

What happens during the execution of `cvWaitKey()`? What are some typical use cases? I saw it in *OpenCV* reference but the documentation isn&#39;t clear on its exact purpose.

What does OpenCV&#39;s cvWaitKey( ) function do?

I want to execute another program within C code.
For example, I want to execute a command

    ./foo 1 2 3

`foo` is the program which exists in the same folder, and `1 2 3` are arguments.
`foo` program creates a file which will be used in my code.

How do I do this?

How do I execute an external program within C code in Linux with arguments?

I have the following program:

    int main(int argc, char *argv[])
    {
      int a, b;
      char c1, c2;
      printf(&quot;Enter something: &quot;);
      scanf(&quot;%d&quot;,&amp;a); // line 1
      printf(&quot;Enter other something: &quot;);
      scanf(&quot;%d&quot;, &amp;b); // line 2

      printf(&quot;Enter a char: &quot;);
      scanf(&quot;%c&quot;,&amp;c1); // line 3
      printf(&quot;Enter another char: &quot;);
      scanf(&quot;%c&quot;, &amp;c2); // line 4

      printf(&quot;Done&quot;); // line 5

      system(&quot;PAUSE&quot;);

      return 0;
    }

As I read in the C book, the author says that `scanf()` left a newline character in the buffer, therefore, the program does not stop at line 4 for user to enter the data, rather it stores the new line character in c2 and moves to line 5.

Is that right?

However, does this only happen with `char` data types? Because I did not see this problem with `int` data types as in line 1, 2, 3. Is it right?


scanf() leaves the newline character in the buffer

I want to write a bash function that check if a file has certain properties and returns true or false. Then I can use it in my scripts in the &quot;if&quot;. But what should I return?

    function myfun(){ ... return 0; else return 1; fi;}

then I use it like this:

    if myfun filename.txt; then ...

of course this doesn&#39;t work. How can this be accomplished?

Returning a boolean from a Bash function

I always thought that `&amp;&amp;` operator in Java is used for verifying whether both its boolean operands are `true`, and the `&amp;` operator is used to do Bit-wise operations on two integer types.

Recently I came to know that `&amp;` operator can also be used verify whether both its boolean operands are `true`, the only difference being that it checks the RHS operand even if the LHS operand is false.

Is the `&amp;` operator in Java internally overloaded? Or is there some other concept behind this? 

What is the difference between &amp; and &amp;&amp; in Java?

&gt;https://stackoverflow.com/questions/5554725/which-value-is-better-to-use-boolean-true-or-integer-1

The above topic made me do some experiments with `bool` and `int` in `if` condition. So just out of curiosity I wrote this program:

    int f(int i) 
    {
    	if ( i ) return 99;   //if(int)
    	else  return -99;
    }
    int g(bool b)
    {
    	if ( b ) return 99;   //if(bool)
    	else  return -99;
    }
    int main(){}

`g++ intbool.cpp -S` generates asm code for each functions as follows:

 - asm code for `f(int)`

        __Z1fi:
           LFB0:
     	         pushl	%ebp
           LCFI0:
    	          movl	%esp, %ebp
           LCFI1:
    	          cmpl	$0, 8(%ebp)
    	          je	L2
    	          movl	$99, %eax
    	          jmp	L3
           L2:
    	          movl	$-99, %eax
           L3:
    	          leave
           LCFI2:
    	          ret


 - asm code for `g(bool)`

        __Z1gb:
           LFB1:
    	          pushl	%ebp
           LCFI3:
    	          movl	%esp, %ebp
           LCFI4:
    	          subl	$4, %esp
           LCFI5:
    	          movl	8(%ebp), %eax
    	          movb	%al, -4(%ebp)
    	          cmpb	$0, -4(%ebp)
    	          je	L5
    	          movl	$99, %eax
    	          jmp	L6
           L5:
    	          movl	$-99, %eax
           L6:
    	          leave
           LCFI6:
    	          ret


Surprisingly, `g(bool)` generates more `asm` instructions! Does it mean that `if(bool)` is little slower than `if(int)`? I used to think `bool` is especially designed to be used in conditional statement such as `if`, so I was expecting `g(bool)` to generate less asm instructions, thereby making `g(bool)` more efficient and fast. 

EDIT:

I&#39;m not using any optimization flag as of now. But even absence of it, why does it generate more asm for `g(bool)` is a question for which I&#39;m looking for a reasonable answer. I should also tell you that `-O2` optimization flag generates exactly same asm. But that isn&#39;t the question. The question is what I&#39;ve asked.

---



Which is faster : if (bool) or if(int)?

What are the default values of `boolean` (primitive) and `Boolean` (primitive wrapper) in Java?




Default value of &#39;boolean&#39; and &#39;Boolean&#39; in Java

Does JSON treat these all the same? Or are they a mix of Integers and booleans?   

    var data =
    {
        &quot;zero&quot; : 0,
        &quot;one&quot; : 1,
        &quot;false&quot; : 0,
        &quot;true&quot; : 1,
        &quot;0&quot; : false,
        &quot;1&quot; : true
    }

Content Type	Original Author	Original Content on Stackoverflow
Question	Don Lun	View Question on Stackoverflow
Solution 1 - C++	Andrew Marshall	View Answer on Stackoverflow
Solution 2 - C++	It Grunt	View Answer on Stackoverflow

Does true equal to 1 and false equal to 0?

C++ Problem Overview

C++ Solutions

Solution 1 - C++

Solution 2 - C++

My enum is not a class or namespace

How to call qDebug without the appended spaces and newline?

Attributions