There is no way to change the precision via `to_string()` but the [`setprecision`](http://en.cppreference.com/w/cpp/io/manip/setprecision) IO manipulator could be used instead:

    #include &lt;sstream&gt;

    template &lt;typename T&gt;
    std::string to_string_with_precision(const T a_value, const int n = 6)
    {
        std::ostringstream out;
        out.precision(n);
        out &lt;&lt; std::fixed &lt;&lt; a_value;
        return out.str();
    }


AngularJS clearly states in its documentation that Services are Singletons:

    AngularJS services are singletons

Counterintuitively, `module.factory` also returns a Singleton instance.

Given that there are plenty of use-cases for non-singleton services, what is the best way to implement the factory method to return instances of a Service, so that each time an `ExampleService` dependency is declared, it is satisfied by a different instance of `ExampleService`?

Non-Singleton Services in AngularJS

I&#39;m trying to get set up with an Android development environment using IntelliJ in Ubuntu 12.04. I create an Android Application Module, but when I try to build, I get the following error:

&gt; android-apt-compiler: Cannot run program &quot;/home/jon/Programs/android-sdk-linux/platform-tools/aapt&quot;: java.io.IOException: error=2, No such file or directory

Several hours of scouring the internet hasn&#39;t helped.

By the way, I ran `locate aapt` in the terminal and found that `aapt` is located at `/home/jon/Programs/android-sdk-linux/build-tools/17.0.0/aapt`


Android Hello-World compile error: Intellij cannot find aapt

In C++11, [`std::to_string`][1] defaults to 6 decimal places when given an input value of type `float` or `double`. What is the recommended, or most elegant, method for changing this precision?


  [1]: http://en.cppreference.com/w/cpp/string/basic_string/to_string

Set precision of std::to_string when converting floating point values

<p>In C++11, <a href="http://en.cppreference.com/w/cpp/string/basic_string/to_string" target="_blank" rel="noopener noreferrer"><code>std::to_string</code></a> defaults to 6 decimal places when given an input value of type <code>float</code> or <code>double</code>. What is the recommended, or most elegant, method for changing this precision?</p>


I have a `QString` in my sources. 
So I need to convert it to integer **without &quot;Kb&quot;.** 

I tried `Abcd.toInt()` but it does not work.

    QString Abcd = &quot;123.5 Kb&quot;




How to convert QString to int?

I saw the following code from some legacy codes:

     size_t a = 1 ???- 2 :0;

What does the symbol `???-` mean in C++?  How should I understand it?


What is the meaning of `???-` in C++ code?

I used: 
`setFixedSize(size());`
to stop the window from resizing, but the resize arrows still appear when the mouse is over the border of the window.

Is there a better way to disable window resizing to avoid showing the arrows when crossing the border?

how can I fully disable resizing a window including the resize icon when the mouse hovers the border?

Is this possible to assign a `NaN` to a `double` or `float` in C/C++? Like in JavaScript you do: `a = NaN`. So later you can check if the variable is a number or no.


C/C++ NaN constant (literal)?

Let&#39;s say I have 10 *.hpp and *.cpp files that I need to compile a code. I know that I will need those same files for many different codes. Can I create a &quot;package&quot; with those files that would allow me to simply write:
```c++
#include &lt;mypackage&gt;
```
instead of:
```c++
#include &quot;file1.hpp&quot;
#include &quot;file2.hpp&quot;
...
#include &quot;file10.hpp&quot;
```
I wouldn&#39;t then need to write a makefile every time I need this &quot;package&quot;. 

To be more precise, I use Linux.

How do I create a library?

What is the difference between a null string (`String s = null`) and an empty string (`String s = &quot;&quot;`)? 

This is what I have:

    String s1 = &quot;&quot;; //print statement does not print any thing for s1 but s1.length()=0
    String s2 = null;//print statement prints &quot;null&quot; for s2  but s2.length() gives exception

What does it mean?

Difference between null and empty string

I am using `split(&#39;\n&#39;)` to get lines in one string, and found that `&#39;&#39;.split()` returns an empty list, `[]`, while `&#39;&#39;.split(&#39;\n&#39;)` returns `[&#39;&#39;]`. Is there any specific reason for such a difference?

And is there any more convenient way to count lines in a string?


When splitting an empty string in Python, why does split() return an empty list while split(&#39;\n&#39;) returns [&#39;&#39;]?

In JavaScript, I have a loop that has many iterations, and in each iteration, I am creating a huge string with many `+=` operators. Is there a more efficient way to create a string? I was thinking about creating a dynamic array where I keep adding strings to it and then do a join. Can anyone explain and give an example of the fastest way to do this?


Most efficient way to concatenate strings in JavaScript?

Assuming I have a String `string` like this:

    &quot;abcd=0; efgh=1&quot;

and I want to replace &quot;abcd&quot; by &quot;dddd&quot;. I have tried to do such thing:

    string.replaceAll(&quot;abcd&quot;,&quot;dddd&quot;);

It does not work. Any suggestions? 

EDIT:
To be more specific, I am working in Java and I am trying to parse the HTML document, concretely the content between `&lt;script&gt;` tags. I have already found a way how to parse this content into a string:

     if(tag instanceof ScriptTag){
    	    if(((ScriptTag) tag).getStringText().contains(&quot;DataVideo&quot;)){
    	    	String tagText = ((ScriptTag)tag).getStringText();
          }
    }

Now I have to find a way how to replace one substring by another one. 

How to replace a substring of a string

`std::unique_ptr` has support for arrays, for instance:

    std::unique_ptr&lt;int[]&gt; p(new int[10]);

but is it needed? probably it is more convenient to use `std::vector` or `std::array`.

Do you find any use for that construct?

Is there any use for unique_ptr with array?

I saw code somewhere in which someone decided to copy an object and subsequently move it to a data member of a class. This left me in confusion in that I thought the whole point of moving was to avoid copying. Here is the example:

    struct S
    {
        S(std::string str) : data(std::move(str))
        {}
    };

Here are my questions:

 - Why aren&#39;t we taking an rvalue-reference to `str`?
 - Won&#39;t a copy be expensive, especially given something like `std::string`?
 - What would be the reason for the author to decide to make a copy then a move?
 - When should I do this myself?

Why do we copy then move?

Is it possible to store a parameter pack somehow for a later use?

    template &lt;typename... T&gt;
    class Action {
    private:        
        std::function&lt;void(T...)&gt; f;
        T... args;  // &lt;--- something like this
    public:
        Action(std::function&lt;void(T...)&gt; f, T... args) : f(f), args(args) {}
        void act(){
            f(args);  // &lt;--- such that this will be possible
        }
    }

Then later on:
    
    void main(){
        Action&lt;int,int&gt; add([](int x, int y){std::cout &lt;&lt; (x+y);}, 3, 4);

        //...

        add.act();
    }

How to store variadic template arguments?

I have a class called `Writer` that has a function `writeVector` like so:

    void Drawer::writeVector(vector&lt;T&gt; vec, bool index=true)
    {
        for (unsigned int i = 0; i &lt; vec.size(); i++) {
            if (index) {
                cout &lt;&lt; i &lt;&lt; &quot;\t&quot;;
            }
            cout &lt;&lt; vec[i] &lt;&lt; &quot;\n&quot;;
        }
    }

I&#39;m trying not to have a duplicate code, while still worrying about the performance.
In the function, I&#39;m doing the `if (index)` check on every round of my `for`-loop, even though the result is always the same.
This is against &quot;worrying about the performance&quot;.

I could easily avoid this by placing the check outside of my `for`-loop.
However, I&#39;ll get loads of duplicate code:

    void Drawer::writeVector(...)
    {
        if (index) {
            for (...) {
                cout &lt;&lt; i &lt;&lt; &quot;\t&quot; &lt;&lt; vec[i] &lt;&lt; &quot;\n&quot;;
            }
        }
        else {
            for (...) {
                cout &lt;&lt; vec[i] &lt;&lt; &quot;\n&quot;;
            }
        }
    }

So these are both &quot;bad&quot; solutions for me.
What I&#39;ve been thinking, is two private functions, one of them outs the index and then calls the other.
The other one only outs the value.
However, I can&#39;t figure out how to use it with my program, I&#39;d still need the `if` check to see which one to call...

According to the problem, polymorphism seems like a correct solution.
But I can&#39;t see how should I use it here.
What would be the preferred way to solve this kind of problem?

This is not a real program, **I&#39;m just interested in learning how this kind of problem should be solved.**

Avoiding if statement inside a for loop?

I use gcc 4.8.1 from http://hpc.sourceforge.net on Mac OSX Mountain Lion. I am trying to compile a C++ program which uses the `to_string` function in `&lt;string&gt;`. I need to use the flag `-std=c++11` every time:

    g++ -std=c++11 -o testcode1 code1.cpp

Is there a way to include this flag by default?

How do I enable C++11 in gcc?

I have been trying to make the answer this prints out to be to two decimal places. All the math involved has to stay at that format of two decimal places. I have tried a few things and I am not sure what to change to make this work.  


    double pdt1 = 239.99;
    double pdt1Total;
    double pdt2 = 129.75;
    double pdt2Total;
    double pdt3 = 99.95;
    double pdt3Total;
    double pdt4 = 350.89;
    double pdt4Total;
    double wage = 200;
    double percentage = 9;
    double total;
    double answer;
    double i = 100;
    double a;
    double b;
    double c;
    double d;

    
    Console.Write(&quot;Enter number sold of product #1: &quot;);
    a = Convert.ToInt32(Console.ReadLine());
      
    Console.Write(&quot;Enter number sold of product #2: &quot;);
    b = Convert.ToInt32(Console.ReadLine());

    Console.Write(&quot;Enter number sold of product #3: &quot;);
    c = Convert.ToInt32(Console.ReadLine());

    Console.Write(&quot;Enter number sold of product #4: &quot;);
    d = Convert.ToInt32(Console.ReadLine());

    

    pdt1Total = a * pdt1;
    pdt2Total = b * pdt2;
    pdt3Total = c * pdt3;
    pdt4Total = d * pdt4;

    total = (pdt1Total + pdt2Total + pdt3Total + pdt4Total);
    
     
 
    string.Format(&quot;{0:0.00}&quot;, total);
    string.Format(&quot;{0:0.00}&quot;, answer = (total * percentage / i) + wage);
    
   
    Console.WriteLine(&quot;Earnings this week: &quot;+answer+&quot;&quot;);

Formatting a double to two decimal places

Let:

    double d = 0.1;
    float f = 0.1;

should the expression

    (f &gt; d)

return `true` or `false`?

Empirically, the answer is `true`. However, I expected it to be `false`.  

As `0.1` cannot be perfectly represented in binary, while double has `15` to `16` decimal digits of precision, and float has only `7`. So, they both are less than `0.1`, while the double is more close to `0.1`.

I need an exact explanation for the `true`.

0.1 float is greater than 0.1 double. I expected it to be false

I am creating for fun, but I still want to approach it seriously, a site which hosts various tests. With these tests I hope to collect statistical data.

Some of the data will include the percentage of the completeness of the tests as they are timed. I can easily compute the percentage of the tests but I would like true data to be returned as I store the various different values concerning the tests on completion.

Most of the values are, in PHP floats, so my question is, if I want true statistical data should I store them in MYSQL as FLOAT, DOUBLE or DECIMAL. 

I would like to utilize MYSQL&#39;S functions such as `AVG()` and `LOG10()` as well as `TRUNCATE()`. For MYSQL to return true data based off of my values that I insert, what should I use as the database column choice.

I ask because some numbers may or may not be floats such as, 10, 10.89, 99.09, or simply 0.
But I would like true and valid statistical data to be returned.

Can I rely on floating point math for this?

**EDIT**

I know this is a generic question, and I apologise extensively, but for non mathematicians like myself, also I am not a MYSQL expert, I would like an opinion of an expert in this field.

I have done my research but I still feel I have a clouded judgement on the matter. Again I apologise if my question is off topic or not suitable for this site.

Storing statistical data, do I need DECIMAL, FLOAT or DOUBLE?

I want the absolute-value from a negative double - and I thought the `abs`-function was as easy to use as in java - but NOT!

It seems that the `abs`-function returns an int because I have the value 3.8951 and the output is 3.000000

    double d1 = abs(-3.8951);
    printf(&quot;d1: ...%lf&quot;, d1);

How can I fix this problem? That is - I want the absolute value of a `double`.

How to get absolute value from double - c-language

My question is that

I have a size_t data, but now I want to convert it to double or int.

If I do something like 

     size_t data = 99999999;
     int convertdata = data;

the compiler will report warning. because it maybe overflow.

Do you have some method like the boost or some other method to do the convert?


How to cast the size_t to double or int C++


I am facing an issue related to converting `double` to `float`. Actually, I store a float type, `23423424666767`, in a database, but when we get data from the database in the below code, `getInfoValueNumeric()`, it&#39;s of `double` type. The value we get is in the `2.3423424666767E13` form.

So how do we get a `float` format data like `23423424666767`?

`2.3423424666767E13 to 23423424666767 `

    public void setInfoValueNumeric(java.lang.Double value) {
        setValue(4, value);
    }


    @javax.persistence.Column(name = &quot;InfoValueNumeric&quot;, precision = 53)
    public java.lang.Double getInfoValueNumeric() {
        return (java.lang.Double) getValue(4);
    }





Content Type	Original Author	Original Content on Stackoverflow
Question	learnvst	View Question on Stackoverflow
Solution 1 - C++	hmjd	View Answer on Stackoverflow

Set precision of std::to_string when converting floating point values

C++ Problem Overview

C++ Solutions

Solution 1 - C++

Android Hello-World compile error: Intellij cannot find aapt

Non-Singleton Services in AngularJS

Attributions