Typically to &#39;reset&#39; a stringstream you need to both reset the underlying sequence to an empty string with `str` and to clear any fail and eof flags with `clear`.

    parser.str( std::string() );
    parser.clear();

Typically what happens is that the first `&gt;&gt;` reaches the end of the string and sets the eof bit, although it successfully parses the first short. Operations on the stream after this immediately fail because the stream&#39;s eof bit is still set.

In my ASP.NET MVC app, I am rendering a checkbox using the following code:

    &lt;%= Html.CheckBoxFor(i=&gt;i.ReceiveRSVPNotifications) %&gt;

Now, I see that this renders *both* the checkbox input tag and a hidden input tag. The problem that I am having is when I try retrieve the value from the checkbox using the FormCollection:

    FormValues[&quot;ReceiveRSVPNotifications&quot;]

I get the value &quot;true,false&quot;. When looking at the rendered HTML, I can see the following:

     &lt;input id=&quot;ReceiveRSVPNotifications&quot; name=&quot;ReceiveRSVPNotifications&quot; value=&quot;true&quot; type=&quot;checkbox&quot;&gt;
     &lt;input name=&quot;ReceiveRSVPNotifications&quot; value=&quot;false&quot; type=&quot;hidden&quot;&gt;

So the FormValues collection seems to join these two values since they have the same name.

Any Ideas?

Why does the CheckBoxFor render an additional input tag, and how can I get the value using the FormCollection?

It looks the same for me,but I&#39;m not sure,

because there are many projects that uses `dirname(__FILE__)`.



Is there any difference between __DIR__ and dirname(__FILE__) in PHP?

    stringstream parser;
    
    parser &lt;&lt; 5;
    short top = 0;
    parser &gt;&gt; top;
    parser.str(&quot;&quot;); //HERE I&#39;M RESETTING parser
    
    parser &lt;&lt; 6; //DOESN&#39;T PUT 6 INTO parser
    short bottom = 0;
    parser &gt;&gt; bottom;

Why doesn&#39;t it work?

How to clear stringstream?

<pre><code class="hljs language-ini">stringstream parser;

parser &#x3C;&#x3C; 5;
short top = 0;
parser >> top;
parser.str(""); //HERE I'M RESETTING parser

parser &#x3C;&#x3C; 6; //DOESN'T PUT 6 INTO parser
short bottom = 0;
parser >> bottom;
</code></pre>
Why doesn't it work?

In the sake of debugging purposes, can I get the line number in **C**/C++ compilers?
(standard way or specific ways for certain compilers)

e.g

    if(!Logical)
        printf(&quot;Not logical value at line number %d \n&quot;,LineNumber);
        // How to get LineNumber without writing it by my hand?(dynamic compilation)



C/C++ line number

I have a map where I&#39;d like to perform a call on every data type object member function. I yet know how to do this on any sequence but, is it possible to do it on an associative container?

The closest answer I could find was this: [Boost.Bind to access std::map elements in std::for_each][1]. But I cannot use boost in my project so, is there an STL alternative that I&#39;m missing to boost::bind?

If not possible, I thought on creating a temporary sequence for pointers to the data objects and then, call for_each on it, something like this:

    class MyClass
    {
    public:
     void Method() const;
    }
    
    std::map&lt;int, MyClass&gt; Map;
    //...
    
    std::vector&lt;MyClass*&gt; Vector;
    std::transform(Map.begin(), Map.end(), std::back_inserter(Vector), std::mem_fun_ref(&amp;std::map&lt;int, MyClass&gt;::value_type::second));
    std::for_each(Vector.begin(), Vector.end(), std::mem_fun(&amp;MyClass::Method));

It looks too obfuscated and I don&#39;t really like it. Any suggestions?

  [1]: https://stackoverflow.com/questions/2311752/boost-bind-to-access-stdmap-elements-in-stdfor-each


Use of for_each on map elements

[This note][1] says:

&gt; [`-ansi`][2]: tells the compiler to implement the ANSI language option. This turns
&gt; off certain &quot;features&quot; of GCC which
&gt; are incompatible with the ANSI
&gt; standard.
&gt;
&gt; [`-pedantic`][3]: used in conjunction with `-ansi`, this tells the compiler to be adhere strictly to the ANSI standard,
&gt; rejecting any code which is not
&gt; compliant.

First things first:

* What is the purpose of the `-pedantic` and `-ansi` options of the GCC/G++ compiler (I couldn&#39;t understand the above description)?
* What are the right circumstances for using these two options?
* When should I use them?
* Are they important?

  [1]: http://web.mit.edu/10.001/Web/Tips/tips_on_gcc.html
  [2]: https://gcc.gnu.org/onlinedocs/gcc/C-Dialect-Options.html#index-ANSI-support
  [3]: https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html#index-pedantic-1


What is the purpose of using -pedantic in the GCC/G++ compiler?

What is the difference between [`printf()`][1] and [`cout`][2] in C++?

  [1]: http://en.cppreference.com/w/cpp/io/c/fprintf
  [2]: http://en.cppreference.com/w/cpp/io/basic_ostream

&#39;printf&#39; vs. &#39;cout&#39; in C++

I need to go through a set and remove elements that meet a predefined criteria.

This is the test code I wrote:

    #include &lt;set&gt;
    #include &lt;algorithm&gt;

    void printElement(int value) {
        std::cout &lt;&lt; value &lt;&lt; &quot; &quot;;
    }

    int main() {
        int initNum[] = { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 };
        std::set&lt;int&gt; numbers(initNum, initNum + 10);
        // print &#39;0 1 2 3 4 5 6 7 8 9&#39;
        std::for_each(numbers.begin(), numbers.end(), printElement);

        std::set&lt;int&gt;::iterator it = numbers.begin();

        // iterate through the set and erase all even numbers
        for (; it != numbers.end(); ++it) {
            int n = *it;
            if (n % 2 == 0) {
                // wouldn&#39;t invalidate the iterator?
                numbers.erase(it);
            }
        }

        // print &#39;1 3 5 7 9&#39;
        std::for_each(numbers.begin(), numbers.end(), printElement);

        return 0;
    }

At first, I thought that erasing an element from the set while iterating through it would invalidate the iterator, and the increment at the for loop would have undefined behavior. Even though, I executed this test code and all went well, and I can&#39;t explain why.

**My question:**
Is this the defined behavior for std sets or is this implementation specific? I am using gcc 4.3.3 on ubuntu 10.04 (32-bit version), by the way.

Thanks!

**Proposed solution:**

Is this a correct way to iterate and erase elements from the set?

    while(it != numbers.end()) {
        int n = *it;
        if (n % 2 == 0) {
            // post-increment operator returns a copy, then increment
            numbers.erase(it++);
        } else {
            // pre-increment operator increments, then return
            ++it;
        }
    }

**Edit: PREFERED SOLUTION**

I came around a solution that seems more elegant to me, even though it does exactly the same.

    while(it != numbers.end()) {
        // copy the current iterator then increment it
        std::set&lt;int&gt;::iterator current = it++;
        int n = *current;
        if (n % 2 == 0) {
            // don&#39;t invalidate iterator it, because it is already
            // pointing to the next element
            numbers.erase(current);
        }
    }

If there are several test conditions inside the while, each one of them must increment the iterator. I like this code better because the iterator is incremented **only in one place**, making the code less error-prone and more readable.

Deleting elements from std::set while iterating

When would I use `std::istringstream`, `std::ostringstream` and `std::stringstream` and why shouldn&#39;t I just use `std::stringstream` in every scenario (are there any runtime performance issues?).

Lastly, is there anything bad about this (instead of using a stream at all):

    std::string stHehe(&quot;Hello &quot;);
  
    stHehe += &quot;stackoverflow.com&quot;;
    stHehe += &quot;!&quot;;
    



What&#39;s the difference between istringstream, ostringstream and stringstream? / Why not use stringstream in every case?

Why does this line give the error `Error: incomplete type is not allowed`?

    stringstream ss;

Incomplete type is not allowed: stringstream

    int main()
    {
       std::stringstream s1(&quot;This is my string.&quot;);
       std::stringstream s2 = s1; // error, copying not allowed
    }

I couldn&#39;t find a reason as to why i can&#39;t copy stringstream. could you provide some reference?

Why copying stringstream is not allowed?

How do I &quot;reset&quot; the state of a stringstream to what it was when I created it?


    int firstValue = 1;
    int secondValue = 2;

    std::wstringstream ss;

	ss &lt;&lt; &quot;Hello: &quot; &lt;&lt; firstValue;

	std::wstring firstText(ss.str());

	//print the value of firstText here


    //How do I &quot;reset&quot; the stringstream here?
    //I would like it behave as if I had created
    // stringstream ss2 and used it below.


	ss &lt;&lt; &quot;Bye: &quot; &lt;&lt; secondValue;

	std::wstring secondText(ss.str());

	//print the value of secondText here

resetting a stringstream

I want to be able to build a string from a class that I create that derives from `Stream`. Specifically, I want to be able to write code like this:

    void Print(Stream stream) {
        // Some code that operates on a Stream.
    }
    
    void Main() {
        StringStream stream = new StringStream();
        Print(stream);
        string myString = stream.GetResult();
    }

Can I create a class called `StringStream` that makes this possible? Or is such a class already available?

**Update:** In my example, the method `Print` is provided in a third-party external DLL. As you can see, the argument that `Print` expects is a `Stream`. After printing to the `Stream`, I want to be able to retrieve its content as a string.

Content Type	Original Author	Original Content on Stackoverflow
Question	There is nothing we can do	View Question on Stackoverflow
Solution 1 - C++	CB Bailey	View Answer on Stackoverflow

How to clear stringstream?

C++ Problem Overview

C++ Solutions

Solution 1 - C++

Is there any difference between DIR and dirname(FILE) in PHP?

Why does the CheckBoxFor render an additional input tag, and how can I get the value using the FormCollection?

Attributions