    #include &lt;boost/algorithm/string/join.hpp&gt;
    #include &lt;vector&gt;
    #include &lt;iostream&gt;
    
    int main()
    {
        std::vector&lt;std::string&gt; list;
        list.push_back(&quot;Hello&quot;);
        list.push_back(&quot;World!&quot;);
    
        std::string joined = boost::algorithm::join(list, &quot;, &quot;);
        std::cout &lt;&lt; joined &lt;&lt; std::endl;
    }

Output:

    Hello, World!


    std::vector&lt;std::string&gt; MyStrings;
    MyStrings.push_back(&quot;Hello&quot;);
    MyStrings.push_back(&quot;World&quot;);
    std::string result = boost::algorithm::join(MyStrings, &quot;,&quot;);
    
    std::cout &lt;&lt; result; // prints &quot;Hello,World&quot;



Is null an Object?

I see that date comparisons can be done and there&#39;s also `datetime.timedelta()`, but I&#39;m struggling to find out how to check if the current time (`datetime.datetime.now()`) is earlier, later or the same than a specified time (e.g. 8am) regardless of the date.

How to compare times of the day?

I recently wanted to use &lt;a href=&quot;http://www.boost.org/doc/libs/1_41_0/doc/html/string_algo/reference.html#header.boost.algorithm.string.join_hpp&quot;&gt; boost::algorithm::join &lt;/a&gt;but I couldn&#39;t find any usage examples and I didn&#39;t want to invest a lot of time learning the Boost Range library just to use this one function.  

Can anyone provide a good example of how to use join on a container of strings?  Thanks.

A good example for boost::algorithm::join

<p>I recently wanted to use <a href="<a href=" http:="" www.boost.org="" doc="" libs="" 1_41_0="" html="" string_algo="" reference.html#header.boost.algorithm.string.join_hpp&#x26;quot;&#x22;="">http://www.boost.org/doc/libs/1_41_0/doc/html/string_algo/reference.html#header.boost.algorithm.string.join_hpp"</a>> boost::algorithm::join but I couldn't find any usage examples and I didn't want to invest a lot of time learning the Boost Range library just to use this one function.</p>
<p>Can anyone provide a good example of how to use join on a container of strings?  Thanks.</p>


Does it ever make sense to check if *this* is null?

Say I have a class with a method; inside that method, I check `this == NULL`, and if it is, return an error code.

If *this* is null, then that means the object is deleted. Is the method even able to return anything?

**Update:** I forgot to mention that the method can be called from multiple threads and it may cause the object to be deleted while another thread is inside the method.

Checking if this is null

What is `uintptr_t` and what can it be used for?


What is uintptr_t data type

The following code gives me a segmentation fault when run on a 2Gb machine, but works on a 4GB machine.


    int main()
    {
       int c[1000000];
       cout &lt;&lt; &quot;done\n&quot;;
       return 0;
    }

The size of the array is just 4Mb. Is there a limit on the size of an array that can be used in c++?



Segmentation fault on large array sizes

&lt;a href=&quot;https://stackoverflow.com/questions/1310344/why-use-when-converting-int-to-bool&quot;&gt;Extends&lt;/a&gt;.

I thought I was being cool when I did something like:

&lt;pre&gt;
bool hasParent()
{
  return this-&amp;gt;parentNode ;
}
&lt;/pre&gt;

Even with a (bool) cast, the warning still doesn&#39;t go away.

Where this-&amp;gt;parentNode is NULL when there is no parent node.

But I&#39;m getting:

&lt;pre&gt;
warning C4800: &#39;Node *&#39; : forcing value to bool &#39;true&#39; or &#39;false&#39; (performance warning)
&lt;/pre&gt;

What&#39;s the deal, yo?  Why is that a performance warning?  I thought it&#39;d be more efficient to not write something like:

&lt;pre&gt;

bool hasParent()
{
  if( this-&amp;gt;parentNode )
    return true ;
  else
    return false ;
}
&lt;/pre&gt;

But the second version generates no warnings and the compiler seems a lot happier.  Which is faster though?

Why is there a performance warning on cast pointer to bool?

Exception handling (EH) seems to be the current standard, and by searching the web, I can not find any novel ideas or methods that try to improve or replace it (well, some variations exist, but nothing novel).

Though most people seem to ignore it or just accept it, EH **has** some huge drawbacks: exceptions are invisible to the code and it creates many, many possible exit points. Joel on software wrote an [article about it][1]. The comparison to `goto` fits perfect, it made me think again about EH.

I try to avoid EH and just use return values, callbacks or whatever fits the purpose. But **when you have to write reliable code, you just can&#39;t ignore EH these days**: It starts with the `new`, which may throw an exception, instead of just returning 0 (like in the old days). This makes about any line of C++ code _vulnerable_ to an exception. And then more places in the C++ foundational code throw exceptions... std lib does it, and so on.

This feels like **walking on shaky grounds**.. So, now we are forced to take care about exceptions!

But its hard, its really hard. You have to learn to write exception safe code, and even if you have some experience with it, it will still be required to double check any single line of code to be safe! Or you start to put try/catch blocks everywhere, which clutters the code until it reaches a state of unreadability.

EH replaced the old clean deterministical approach (return values..), which had just a few but understandable and easily solveable drawbacks with an approach that creates many possible exit points in your code, and if you start writing code that catches exceptions (what you are forced to do at some point), then it even creates a multitude of paths through your code (code in the catch blocks, think about a server program where you need logging facilities other than std::cerr ..). EH has advantages, but that&#39;s not the point.

My actual questions:

  - Do you really write exception safe code?
  - Are you sure your last &quot;production ready&quot; code is exception safe?
  - Can you even be sure, that it is?
  - Do you know and/or actually use alternatives that work?



  [1]: http://www.joelonsoftware.com/items/2003/10/13.html

Do you (really) write exception safe code?

How would it be possible to generate a random, unique string using numbers and letters for use in a verify link? Like when you create an account on a website, and it sends you an email with a link, and you have to click that link in order to verify your account

How can I generate one of those using PHP?

How to generate a random, unique, alphanumeric string?

Note: I&#39;m sorry if this is an extremely simple question but I&#39;m somewhat obsessive compulsive over the formatting of my code.

I have a class that has a function that returns a string that will make up the body text of an email. I want this text formatted so it looks right in the email, but also so it doesn&#39;t make my code look funky. Here&#39;s what I mean:

    class Something
    {
        public function getEmailText($vars)
        {
            $text = &#39;Hello &#39; . $vars-&gt;name . &quot;,
    
    The second line starts two lines below.
    
    I also don&#39;t want any spaces before the new line, so it&#39;s butted up against the left side of the screen.&quot;;
            return $text;
        }
    }

but it could also be written as:

    public function getEmailText($vars)
    {
        $text = &quot;Hello {$vars-&gt;name},\n\rThe second line starts two lines below.\n\rI also don&#39;t want any spaces before the new line, so it&#39;s butted up against the left side of the screen.&quot;;
        return $text;
    }

but what&#39;s the deal with new lines and carriage returns? What&#39;s the difference? Is `\n\n` the equivalent of `\r\r` or `\n\r`? Which should I use when I&#39;m creating a line gap between lines?

Then there&#39;s the option of output buffering and heredoc syntax.

How do you deal with using long multiline strings in your objects?

Best Practices: working with long, multiline strings in PHP?

&gt; **Possible Duplicate:** &lt;br/&gt;
&gt; [Enum with strings](https://stackoverflow.com/questions/630803/enum-with-strings)

Is it possible to have string constants in enum like the following?

          enum{name1=&quot;hmmm&quot; name2=&quot;bdidwe&quot;}

If it is not, what is the best way to do so?

I tried it, but it&#39;s not working for string so right now I am grouping all related constants in one class like

          class operation
          {
              public const string  name1=&quot;hmmm&quot;;
              public const string  name2=&quot;bdidwe&quot;
          }





How can I use enum in C# for storing string constants?

I just created sample BB app, which can allow to choose the date.

    DateField curDateFld = new DateField(&quot;Choose Date: &quot;,
      System.currentTimeMillis(), DateField.DATE | DateField.FIELD_LEFT);

After choosing the date, I need to convert that long value to String, so that I can easily store the date value somewhere in database.
I am new to Java and Blackberry development.

    long date = curDateFld.getDate();

How should I convert this long value to String? Also I want to convert back to long from String. I think for that I can use `long l = Long.parseLong(&quot;myStr&quot;);`?


How to convert / cast long to String?

According to [String#intern()][1], `intern` method is supposed to return the String from the String pool if the String is found in String pool, otherwise a new string object will be added in String pool and the reference of this String is returned. 

So i tried this: 

    String s1 = &quot;Rakesh&quot;;
    String s2 = &quot;Rakesh&quot;;
    String s3 = &quot;Rakesh&quot;.intern();
    
    if ( s1 == s2 ){
    	System.out.println(&quot;s1 and s2 are same&quot;);  // 1.
    }
    
    if ( s1 == s3 ){
    	System.out.println(&quot;s1 and s3 are same&quot; );  // 2.
    }

I was expecting that `s1 and s3 are same` will be printed as s3 is interned, and `s1 and s2 are same` will not be printed. But the result is: both lines are printed. So that means, by default String constants are interned. But if it is so, then why do we need the `intern` method? In other words when should we use this method?

  [1]: https://docs.oracle.com/javase/9/docs/api/java/lang/String.html#intern--

When should we use intern method of String on String literals

I find [boost::foreach][1] very useful as it saves me a lot of writing. For example, let&#39;s say I want to print all the elements in a list:

    std::list&lt;int&gt; numbers = { 1, 2, 3, 4 };
    for (std::list&lt;int&gt;::iterator i = numbers.begin(); i != numbers.end(); ++i)
       cout &lt;&lt; *i &lt;&lt; &quot; &quot;;

boost::foreach makes the code above much simplier:

    std::list&lt;int&gt; numbers = { 1, 2, 3, 4 };
    BOOST_FOREACH (int i, numbers)
       cout &lt;&lt; i &lt;&lt; &quot; &quot;;

Much better! However I never figured out a way (if it&#39;s at all possible) to use it for `std::map`s. The documentation only has examples with types such as `vector` or `string`.

[1]: http://www.boost.org/doc/libs/1_35_0/doc/html/foreach.html

Is it possible to use boost::foreach with std::map?

I&#39;m trying to create a JSON array using boost property trees. 

The [documentation][1] says: &quot;JSON arrays are mapped to nodes. Each element is a child node with an empty name.&quot;

So I&#39;d like to create a property tree with empty names, then call `write_json(...)` to get the array out. However, the documentation doesn&#39;t tell me how to create unnamed child nodes. I tried `ptree.add_child(&quot;&quot;, value)`, but this yields:

    Assertion `!p.empty() &amp;&amp; &quot;Empty path not allowed for put_child.&quot;&#39; failed

The documentation doesn&#39;t seem to address this point, at least not in any way I can figure out. Can anyone help?


  [1]: http://www.boost.org/doc/libs/1_49_0/doc/html/boost_propertytree/parsers.html#boost_propertytree.parsers.json_parser

Creating JSON arrays in Boost using Property Trees

Are there any downsides with using `make_shared&lt;T&gt;()` instead of using `shared_ptr&lt;T&gt;(new T)`.

[Boost documentation][1] states 

&gt; There have been repeated requests from
&gt; users for a factory function that
&gt; creates an object of a given type and
&gt; returns a shared_ptr to it. Besides
&gt; convenience and style, such a function
&gt; is also exception safe and
&gt; considerably faster because it can use
&gt; a single allocation for both the
&gt; object and its corresponding control
&gt; block, eliminating a significant
&gt; portion of shared_ptr&#39;s construction
&gt; overhead. This eliminates one of the
&gt; major efficiency complaints about
&gt; shared_ptr.

  [1]: http://www.boost.org/doc/libs/1_41_0/libs/smart_ptr/make_shared.html

Are there any downsides with using make_shared to create a shared_ptr

The following code causes cl.exe to crash (MS VS2005).  
I am trying to use boost bind to create a function to a calls a method of myclass:   


    #include &quot;stdafx.h&quot;
    #include &lt;boost/function.hpp&gt;
    #include &lt;boost/bind.hpp&gt;
    #include &lt;functional&gt;
    
    class myclass {
    public:
    	void fun1()       { printf(&quot;fun1()\n&quot;);      }
    	void fun2(int i)  { printf(&quot;fun2(%d)\n&quot;, i); }
    
    	void testit() {
    		boost::function&lt;void ()&gt;    f1( boost::bind( &amp;myclass::fun1, this ) );
    		boost::function&lt;void (int)&gt; f2( boost::bind( &amp;myclass::fun2, this ) ); //fails
    
    		f1();
    		f2(111);
    	}
    };
    
    int main(int argc, char* argv[]) {
    	myclass mc;
    	mc.testit();
    	return 0;
    }


What am I doing wrong?

How to use boost bind with a member function

Is there a version of 64-bit Boost library for VS2008 ?
Or do I have to compile one myself? if, so, does anyone have experience with it?

64-bit version of Boost for 64-bit windows

SQLite only has INNER and LEFT JOIN.

Is there a way to do a FULL OUTER JOIN with SQLite?

FULL OUTER JOIN with SQLite

I have been trying to get this working for quite a while now but it just doesn&#39;t seem to work, maybe it is is not even possible, what i am wanting to do is to perform a MySQL join query using like, such as this example i found...

    SELECT *
    FROM Table1
    INNER JOIN Table2 ON Table1.col LIKE &#39;%&#39; + Table2.col + &#39;%&#39;

but it just doesn&#39;t seem to work at all, any help that can be given would be brilliant, thanks !

MySQL join query using like?

I am trying to create a news page for a website I am working on. I decided that I want to use correct MySQL queries (meaning COUNT(id) and joins instead of more than one query or num_rows.) I&#39;m using a PDO wrapper, that should function fine, and this still fails when run directly through the MySQL CLI application.

Basically, I have 3 tables. One holds the news, one holds the comments and one holds the users. My aim here is to create a page which displays all (will paginate later) the news posts titles, bodies, authors and dates. This worked fine when I used a second query to get the username, but then I decided I&#39;d rather use a JOIN.

So what&#39;s the problem? Well, I need two joins. One is to get the author&#39;s username and the other to get the number of comments. When I simply go for the author&#39;s username, all works as expected. All the rows (there are 2) in the news table are displayed. However, when I added this second LEFT JOIN for the comments row, I end up only receiving one row from news (remember, there are 2,) and COUNT(comments.id) gives me 2 (it should display 1, as I have a comment for each post.)

What am I doing wrong? Why is it only displaying one news post, and saying that it has two comments, when there are two news posts, each with one comment?

    SELECT news.id, users.username, news.title, news.date, news.body, COUNT(comments.id)
    FROM news
    LEFT JOIN users
    ON news.user_id = users.id
    LEFT JOIN comments
    ON comments.news_id = news.id

Also, just to be sure about one other thing, my left join to comments is the correct way to get all posts regardless of whether they have comments or not, correct? Or would that be a right join? Oh, one last thing... if I switch comments.news_id = news.id to news.id = comments.news_id, I get 0 results.

MySQL Multiple Left Joins

Why does this work (returns &quot;one, two, three&quot;):

    var words = [&#39;one&#39;, &#39;two&#39;, &#39;three&#39;];
    $(&quot;#main&quot;).append(&#39;&lt;p&gt;&#39; + words.join(&quot;, &quot;) + &#39;&lt;/p&gt;&#39;);

and this work (returns &quot;the list: 111&quot;):

    var displayIt = function() {
        return &#39;the list: &#39; + arguments[0];
    }   
    $(&quot;#main&quot;).append(&#39;&lt;p&gt;&#39; + displayIt(&#39;111&#39;, &#39;222&#39;, &#39;333&#39;) + &#39;&lt;/p&gt;&#39;);

but not this (returns blank):

    var displayIt = function() {
        return &#39;the list: &#39; + arguments.join(&quot;,&quot;);
    }   
    $(&quot;#main&quot;).append(&#39;&lt;p&gt;&#39; + displayIt(&#39;111&#39;, &#39;222&#39;, &#39;333&#39;) + &#39;&lt;/p&gt;&#39;);

**What do I have to do to my &quot;arguments&quot; variable to be to use .join() on it?**



Why doesn&#39;t .join() work with function arguments?

Suppose I have a table of customers and a table of purchases. Each purchase belongs to one customer. I want to get a list of all customers along with their last purchase in one `SELECT` statement. What is the best practice? Any advice on building indexes?

Please use these table/column names in your answer:

 - customer: `id`, `name`
 - purchase: `id`, `customer_id`, `item_id`, `date`

And in more complicated situations, would it be (performance-wise) beneficial to denormalize the database by putting the last purchase into the customer table?

If the (purchase) `id` is guaranteed to be sorted by date, can the statements be simplified by using something like `LIMIT 1`?

Content Type	Original Author	Original Content on Stackoverflow
Question	Dan Hook	View Question on Stackoverflow
Solution 1 - C++	Tristram Gräbener	View Answer on Stackoverflow
Solution 2 - C++	KeatsPeeks	View Answer on Stackoverflow

A good example for boost::algorithm::join

C++ Problem Overview

C++ Solutions

Solution 1 - C++

Solution 2 - C++

How to compare times of the day?

Is null an Object?

Attributions