    ns::B::*

is a pointer-to-member-variable of `B`. Then `ns::A*` is its type.

So the whole declaration means

*pointer-to-member-variable of `B` of type `ns::A*`*

[The answer by @vsoftco](https://stackoverflow.com/a/33764721/434551) already answers the core of the question. This answer shows how one might use such a `typedef`.

    #include &lt;iostream&gt;
    #include &lt;cstddef&gt;
    
    namespace ns {
    
       struct A {};
    
       struct B
       {
          A* a1;
          A* a2;
       };
    }
    
    struct C {
       typedef ns::A* ns::B::*type;
    };
    
    int main()
    {
       C::type ptr1 = &amp;ns::B::a1;
       C::type ptr2 = &amp;ns::B::a2;
    
       ns::B b1;
       b1.*ptr1 = new ns::A; // Samething as b1.a1 = new ns::A;
    
       return 0;
    }


I&#39;d like to change &quot;app-release.apk&quot; file name to like following when I build an app by using gradle.

&lt;pre&gt;
[format]
(appname of package name)_V(version code)_(yyMMdd)_(R|T)

[explain]
(appname of package name) : example) com.example.myApp -&gt; myApp
(version code) : build version code 2.2.3 -&gt; 223
(yyMMdd) : build date 2015.11.18 -&gt; 151118  
(R|T) : if app is release, &quot;R&quot; but debug is &quot;T&quot;.
&lt;/pre&gt;
If I generate an apk file in release, result is : myApp_V223_151118_R.apk.

How to make a file name like this in gradle?


How to change apk name by using gradle like this format?

Lets say I have:

    var someValues = [1, &#39;abc&#39;, 3, &#39;sss&#39;];

How can I use an arrow function to loop through each and perform an operation on each value?

Loop through array of values with Arrow Function

I&#39;m reading code of a C++ project and it contains some code of the following form:

    namespace ns {
        class A {};
        class B {};
    }

    struct C {
        typedef ns::A* ns::B::* type;
    };

Can someone explain the meaning of the `typedef` line? `type` seems to be some kind of pointer to member of `ns::B` which points to `ns::A`, but I&#39;m not sure.

Class `A` and `B` in the real code are not empty, but I think it&#39;s not relevant here. And here is a [live example](http://coliru.stacked-crooked.com/a/d2956ed3017bf618).

A confusing typedef involves class scope

I'm reading code of a C++ project and it contains some code of the following form:
<pre><code class="hljs language-arduino">namespace ns {
 class A {};
 class B {};
}

struct C {
 typedef ns::A* ns::B::* type;
};
</code></pre>
Can someone explain the meaning of the <code>typedef</code> line? <code>type</code> seems to be some kind of pointer to member of <code>ns::B</code> which points to <code>ns::A</code>, but I'm not sure.
Class <code>A</code> and <code>B</code> in the real code are not empty, but I think it's not relevant here. And here is a <a href="http://coliru.stacked-crooked.com/a/d2956ed3017bf618" target="_blank" rel="noopener noreferrer">live example</a>.

Currently, I am reading the source code of `Protocol Buffer`, and I found one weird `enum` codes defined [here](https://github.com/google/protobuf/blob/master/src/google/protobuf/stubs/scoped_ptr.h#L72-L75)

      ~scoped_ptr() {
        enum { type_must_be_complete = sizeof(C) };
        delete ptr_;
      }

      void reset(C* p = NULL) {
        if (p != ptr_) {
          enum { type_must_be_complete = sizeof(C) };
          delete ptr_;
          ptr_ = p;
        }
      }

Why the `enum { type_must_be_complete = sizeof(C) };` is defined here? what is it used for?

Weird enum in destructor

    void func(const std::function&lt;void()&gt;&amp; f = empty)
    {
        if(f)
            f();
    }
what is the &#39;empty&#39; should be? I use `[](){}` . But technically, that is not empty, the f() will execute.

specify default value of std::function

I&#39;ve been asked in a recent interview about C++ struct fields alignment and theoretized that C and C++ follows the same strategy in struct packing. 

Hovewer, it was the wrong assumption. The interviewer said that in general C and C++ are packing structs in different ways and we should never expect the opposite. IMHO it&#39;s strange statement. There is no `pack &quot;C&quot;` qualifier for structs in C++ for using in bilingual C/C++ header files.

So in practice it could mean that you can&#39;t create a struct in C++ and pass it to a C library because in general its fields will be aligned in a different way and have different offsets. But, in fact, most programmers seriously rely on this interoperability up to the point when they convert a pointer to a C [POD][1] struct to a reference to C++ wrapper around this struct with some helper methods. Can you please clarify this matter?

  [1]: http://en.wikipedia.org/wiki/Plain_old_data_structure


C vs C++ struct alignment

I&#39;m arguing with my boss about this. They say &quot;Yes they can be different.&quot;

Is it possible that `sizeof(T*) != sizeof(const T*)` for a type `T`?

Could it be the case that sizeof(T*) != sizeof(const T*)?

Consider the following code (`p` is of type `unsigned char*` and `bitmap-&gt;width` is of some integer type, exactly which is unknown and depends on which version of some external library we&#39;re using):

    for (unsigned x = 0;  x &lt; static_cast&lt;unsigned&gt;(bitmap-&gt;width);  ++x)
    {
        *p++ = 0xAA;
        *p++ = 0xBB;
        *p++ = 0xCC;
    }

&lt;sub&gt;&lt;s&gt;Is it worth optimizing it [..]&lt;/s&gt;&lt;/sub&gt;

Could there be a case where this could yield more efficient results by writing:

    unsigned width(static_cast&lt;unsigned&gt;(bitmap-&gt;width));
    for (unsigned x = 0;  x &lt; width;  ++x)
    {
        *p++ = 0xAA;
        *p++ = 0xBB;
        *p++ = 0xCC;
    }

... or is this trivial for the compiler to optimize?

&lt;sub&gt;&lt;s&gt;What would you consider to be &quot;better&quot; code?&lt;/s&gt;&lt;/sub&gt;

&lt;sub&gt;*Note from editor (Ike): for those wondering about the strikeout text, the original question, as phrased, was dangerously close to off-topic territory and was very close to being closed in spite of positive feedback. These have been stricken out. Yet please do not punish the answerers who addressed these stricken sections of the question.*&lt;/sub&gt;

In C++, should I bother to cache variables, or let the compiler do the optimization? (Aliasing)

According to [cppreference.com](http://en.cppreference.com/w/cpp/types/size_t) `size_t` is defined in several headers, namely


    &lt;cstddef&gt;
    &lt;cstdio&gt;
    &lt;cstring&gt;
    &lt;ctime&gt;

And, since C++11, also in

    &lt;cstdlib&gt;
    &lt;cwchar&gt; 

First of all, I wonder why this is the case. Isn&#39;t this in contradiction to the [DRY](https://en.wikipedia.org/wiki/Don&#39;t_repeat_yourself) principle?

Which one of the above headers should I include to use `size_t`? Does it matter at all?

Which header should I include for `size_t`?

I was snooping through my MSP430 microcontroller&#39;s header files, and I ran into this in `&lt;setjmp.h&gt;`:

    /* r3 does not have to be saved */
    typedef struct
    {
    	uint32_t __j_pc; /* return address */
    	uint32_t __j_sp; /* r1 stack pointer */
    	uint32_t __j_sr; /* r2 status register */
    	uint32_t __j_r4;
    	uint32_t __j_r5;
    	uint32_t __j_r6;
    	uint32_t __j_r7;
    	uint32_t __j_r8;
    	uint32_t __j_r9;
    	uint32_t __j_r10;
    	uint32_t __j_r11;
    } jmp_buf[1]; /* size = 20 bytes */

I understand that it declares an anonymous struct and typedef&#39;s it to `jmp_buf`, but I can&#39;t figure out what the `[1]` is for. I know it declares `jmp_buf` to be an array with one member (of this anonymous struct), but I can&#39;t imagine what it&#39;s used for. Any ideas?

Content Type	Original Author	Original Content on Stackoverflow
Question	Tien	View Question on Stackoverflow
Solution 1 - C++	vsoftco	View Answer on Stackoverflow
Solution 2 - C++	R Sahu	View Answer on Stackoverflow

A confusing typedef involves class scope

C++ Problem Overview

C++ Solutions

Solution 1 - C++

Solution 2 - C++

Loop through array of values with Arrow Function

How to change apk name by using gradle like this format?

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