Files with a .m extension contain MATLAB code, either in the form of a [script][1] or a [function][2].

Files with a .mat extension contain [MATLAB formatted data][3], and data can be loaded from or written to these files using the functions [`load`][4] and [`save`][5], respectively. You can also access and change variables directly in MAT-files without loading them into memory using the function [`matfile`][6].


  [1]: https://www.mathworks.com/help/matlab/learn_matlab/scripts.html
  [2]: https://www.mathworks.com/help/matlab/matlab_prog/create-functions-in-files.html
  [3]: http://www.mathworks.com/help/matlab/import_export/supported-file-formats.html
  [4]: https://www.mathworks.com/help/matlab/ref/load.html
  [5]: https://www.mathworks.com/help/matlab/ref/save.html
  [6]: https://www.mathworks.com/help/matlab/ref/matfile.html

I used to think that in C99, even if the side-effects of functions `f` and `g` interfered, and although the expression `f() + g()` does not contain a sequence point, `f` and `g` would contain some, so the behavior would be unspecified: either f() would be called before g(), or g() before f().

I am no longer so sure. What if the compiler inlines the functions (which the compiler may decide to do even if the functions are not declared `inline`) and then reorders instructions? May one get a result different of the above two? In other words, is this undefined behavior?

This is not because I intend to write this kind of thing, this is to choose the best label for such a statement in a static analyzer. 


In C99, is f()+g() undefined or merely unspecified?

I have to get the current country in the iPhone settings. Can anyone tell me how to get the current country in iPhone application.

I have to use the current country for parsing the RSS feed in which I need to pass the current country. 

Please help me out to find the country .

Thanks in advance.

Find current country from iPhone device

When I traced my reference MATLAB script, I found files with the `.mat` extension. My questions are:

 1. What is the difference between `.mat` and `.m` files?
 2. How does one open files with the `.mat` extension?


What is the difference between .m and .mat files in MATLAB

<p>When I traced my reference MATLAB script, I found files with the <code>.mat</code> extension. My questions are:</p>
<ol>
<li>What is the difference between <code>.mat</code> and <code>.m</code> files?</li>
<li>How does one open files with the <code>.mat</code> extension?</li>
</ol>


I&#39;m writing 2 functions in matlab, an initialize function and a function to insert items into an array treating it like a doubly-linked list. However, my initialize function only returns &quot;ans =&quot; and the initialized array. How can I have it also set values of my other variables? Here&#39;s my code: 

    function [ array, listp, freep ] = initialize( size )
        array = zeros(size, 3);
        listp = 0;
        freep = 1;
    end

MATLAB - multiple return values from a function?

*This question arose out of something strange that I noticed after investigating [this question][1] further...*

I always understood MATLAB variables to be [double-precision][2] by default. So, if I were to do something like declare a variable with 20 digits after the decimal point:

    &gt;&gt; num = 2.71828182845904553488;
    &gt;&gt; class(num)  % Display the variable type
    ans =
    double

I would expect the last 4 digits to be ignored, since the [floating-point relative accuracy][3] is on the order of 10&lt;sup&gt;-16&lt;/sup&gt;:

    &gt;&gt; eps(num)
    ans =
        4.440892098500626e-016

If I try to display the number with more than 16 digits after the decimal point (using either [`fprintf`][4] or [`sprintf`][5]), I get what I expect to see:

    &gt;&gt; fprintf(&#39;%0.20f\n&#39;, num)
    2.71828182845904550000
    &gt;&gt; sprintf(&#39;%0.20f&#39;, num)
    ans =
    2.71828182845904550000

In other words, digits 17 through 20 are all 0.

But things get weird when I pass `num` to the [variable precision arithmetic function][6] in the [Symbolic Toolbox][7], telling it to represent the number using 21 digits of precision:

    &gt;&gt; vpa(num, 21)
    ans =
    2.71828182845904553488

**WHAT?!** Those last 4 digits have reappeared! Shouldn&#39;t they have been lost when the original number I entered was stored as a double-precision variable `num`? Since `num` is a double-precision variable when it is passed to `vpa`, how did `vpa` know what they were?

My best guess as to what is happening is that MATLAB internally represents `num` with more precision than a double since I initialized it to a number with more digits past the decimal point than a double-precision variable could handle. Is this really what is happening, or is something else going on?

&lt;br&gt;

----------


**BONUS:** And here&#39;s an additional source of confusion if you don&#39;t already have a migraine from the above...

    &gt;&gt; num = 2.71828182845904553488;  % Declare with 20 digits past the decimal
    &gt;&gt; num = 2.718281828459045531;    % Re-declare with 18 digits past the decimal
    &gt;&gt; vpa(num, 21)
    ans =
    2.71828182845904553488  % It&#39;s the original 20-digit number!!!


  [1]: https://stackoverflow.com/q/4222257/52738
  [2]: https://en.wikipedia.org/wiki/Double-precision_floating-point_format
  [3]: https://www.mathworks.com/help/matlab/ref/eps.html
  [4]: https://www.mathworks.com/help/matlab/ref/fprintf.html
  [5]: https://www.mathworks.com/help/matlab/ref/sprintf.html
  [6]: https://www.mathworks.com/help/symbolic/vpa.html
  [7]: https://www.mathworks.com/help/symbolic/index.html

In MATLAB, are variables REALLY double-precision by default?

For data that is known to have seasonal, or daily patterns I&#39;d like to use fourier analysis be used to make predictions. After running fft on time series data, I obtain coefficients. How can I use these coefficients for prediction? 

I believe FFT assumes all data it receives constitute one period, then, if I simply regenerate data using ifft, I am also regenerating the continuation of my function, so can I use these values for future values? 

Simply put: I run fft for t=0,1,2,..10 then using ifft on coef, can I use regenerated time series for t=11,12,..20 ?  

Using fourier analysis for time series prediction

I have nine open figures in matlab (generated by another function) and I want to print them all to file. Does anyone know how to grab the handles of all open figures in MATLAB? 

I know about `gcf` but it doesn&#39;t seem to do what I want. 

How do I get the handles of all open figures in MATLAB

I am looking for a definitive answer to MATLAB&#39;s parfor for Python (Scipy, Numpy).

Is there a solution similar to parfor? If not, what is the complication for creating one?

UPDATE: Here is a typical numerical computation code that I need speeding up

    import numpy as np

    N = 2000
    output = np.zeros([N,N])
    for i in range(N):
        for j in range(N):
            output[i,j] = HeavyComputationThatIsThreadSafe(i,j)

An example of a heavy computation function is:

    import scipy.optimize
    
    def HeavyComputationThatIsThreadSafe(i,j):
        n = i * j
        
        return scipy.optimize.anneal(lambda x: np.sum((x-np.arange(n)**2)), np.random.random((n,1)))[0][0,0]


Parfor for Python

How can I find all the files in a directory having the extension `.txt` in python?

Find all files in a directory with extension .txt in Python

I got some folders created by malware whose name ended with a dot like `C:\a.\` or `C:\b.\`, etc.

I found a solution that can remove such folder with command `rd /q /s &quot;C:\a.\&quot;` but if I call win API [`RemoveDirectory`][1], it returns `ERROR_FILE_NOT_FOUND`.

And I just wonder how to write a function to delete such directory, thanks

I test on my own Windows XP SP3 system like this

create a folder `C:\&gt;mkdir a..\\\` and I cannot double click to access this folder. and I can remove with command  `rd /q /s &quot;C:\a.\&quot;`

what Windows system API(s) that `rd /q /s` command call? 
 

  [1]: http://msdn.microsoft.com/en-us/library/aa365488(VS.85).aspx

How to delete a folder that name ended with a dot (&quot;.&quot;)?

Say I have some simple class and once it&#39;s instantiated as an object I want to be able to serialize its contents to a file, and retrieve it by loading that file at some later time... I&#39;m not sure where to start here, **what do I need to do to serialize this object to a file?**

    public class SimpleClass {
       public string name;
       public int id;
       public void save() {
           /* wtf do I do here? */
       }
       public static SimpleClass load(String file) {
           /* what about here? */
       }
    }

This is probably the easiest question in the world, because this is a really simple task in .NET, but in Android I&#39;m pretty new so I&#39;m completely lost.

How do I serialize an object and save it to a file in Android?

How can I open a file, Stud.txt, and then replace any occurences of &quot;A&quot; with &quot;Orange&quot;?

Replace string within file contents

In my remote MySQL, when I try to execute this query,
I am getting the MySQL Error Code : 13.

Query -

    LOAD DATA INFILE 
    &#39;/httpdocs/.../.../testFile.csv&#39;
    INTO TABLE table_temp
    FIELDS TERMINATED BY &#39;,&#39;
    LINES TERMINATED BY &#39;\\r \\n&#39;
    (sku, qty);

Error Code : `13 Can&#39;t get stat of &#39;/httpdocs/.../.../testFile.csv&#39; (Errcode: 2)`

a. The database userlogin has all the grant priviliges.

    CREATE USER &#39;userName&#39;@&#39;%&#39; IDENTIFIED BY &#39;************&#39;;
    
    GRANT ALL PRIVILEGES ON * . * TO &#39;userName&#39;@&#39;%&#39; IDENTIFIED BY &#39;************&#39; WITH GRANT OPTION MAX_QUERIES_PER_HOUR 0 MAX_CONNECTIONS_PER_HOUR 0 MAX_UPDATES_PER_HOUR 0 MAX_USER_CONNECTIONS 0 ;
    
    GRANT ALL PRIVILEGES ON `userName\_%` . * TO &#39;userName&#39;@&#39;%&#39;;

b. I have also set the file and folder permission to chmod 777 (rwxrwxrwx)
   using FTP Tool





LOAD DATA INFILE Error Code : 13

I have seen `.gnu`, `.plt`, and `.gplot` as file extensions for gnuplot scripts.

I know Linux doesn&#39;t care about file extensions, but what extension most universally declares to human beings &quot;*I am a gnuplot script!*&quot;?

Is there a standard file extension for gnuplot files?

I&#39;m working on a certain program where I need to do different things depending on the extension of the file. Could I just use this?


    if m == *.mp3
       ...
    elif m == *.flac
       ...

How can I check the extension of a file?

On GitHub, several projects have `README.md` files. It seems like a simple format file to express text and pictures. 

I guess there is an editor or syntax explanation somewhere.

Where can I find an introduction to `.md` files?

What file uses .md extension and how should I edit them?

Just wondering which programming languages is used on the web pages with the extension &quot;.do&quot;


Which programming language has extension .do

Usually a C# project has a .csproj file associated with it. What is that file for? What data does it contain? 

Content Type	Original Author	Original Content on Stackoverflow
Question	user477670	View Question on Stackoverflow
Solution 1 - Matlab	gnovice	View Answer on Stackoverflow

What is the difference between .m and .mat files in MATLAB

Matlab Problem Overview

Matlab Solutions

Solution 1 - Matlab

Find current country from iPhone device

In C99, is f()+g() undefined or merely unspecified?

Attributions