Just found the [IGCC][1] (Interactive GCC) REPL.  I like it.

Example:

    ./igcc

    g++&gt; int a = 1, b = 2;
    g++&gt; printf(&quot;%d\n&quot;, a + b);
    3
    g++&gt; 

And it gives you compile errors like this:

    g++&gt; c = 3;
    [Compile error - type .e to see it.]
    g++&gt; .e
    &lt;stdin&gt;:14:1: error: use of undeclared identifier &#39;c&#39;
    c = 3;
    ^

(SF download: http://sourceforge.net/projects/igcc/files/)


  [1]: http://www.artificialworlds.net/wiki/IGCC/IGCC

[gdb][1] makes a pretty good REPL.  You can&#39;t define new functions there, but you can evaluate expressions (including those with side effects).


  [1]: http://sources.redhat.com/gdb/

Seems like the code of *c-repl* can now be found at a [Github repository](https://github.com/martine/c-repl). It seems to be a dead project, though (last commit was 3 years ago), so I&#39;d suggest looking into alternatives as well:

 * CINT [Archived old official page from web.archive.org][1] or [&quot;Masaharu Goto&quot; CINT page][2]
 * ccons [Github][3] or [code.google][4]
 * [Cling][5], successor of CINT, but only supports C++ (which might or might not be a problem, depending on what features you need)

[1]: https://web.archive.org/web/20200504034257/http://root.cern.ch/cint
[2]: http://www.hanno.jp/gotom/Cint.html
[3]: https://github.com/asvitkine/ccons
[4]: http://code.google.com/p/ccons/
[5]: https://root.cern/cling/

I have not yet been able to find a list of all the built-in Exception sub classes in PHP.  I&#39;d rather use built in ones when they make sense, before creating my own exception subclasses.

For example, I know InvalidArgumentException exists, but there appears to be nothing comparable to Java&#39;s NullPointerException.

Does anyone have or can link to a list of the available Exception subclasses in PHP?

What Exception subclasses are built into PHP?

I&#39;m trying to get my custom validation to work on `create`. But when I do a `find` then `save`, rails treats it as `create` and runs the custom validation. How do I get the validations to only work when creating a new record on not on the update of a found record?

Rails - Validate on Create Only

I am on osx. I  found this 
http://neugierig.org/software/c-repl/
but the links on that page for code seem to be broken.

Is there a REPL for C programming?

<p>I am on osx. I  found this
<a href="http://neugierig.org/software/c-repl/" target="_blank" rel="noopener noreferrer">http://neugierig.org/software/c-repl/</a>
but the links on that page for code seem to be broken.</p>


The title of the question might be a bit strange, but the thing is that, as far as I know, there is nothing that speaks against tail call optimization at all. However, while browsing open source projects, I already came across a few functions that actively try to stop the compiler from doing a tail call optimization, for example the implementation of [CFRunLoopRef](http://opensource.apple.com/source/CF/CF-635.21/CFRunLoop.c) which is full of such *hacks*. For example:

    static void __CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__() __attribute__((noinline));
    static void __CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__(CFRunLoopObserverCallBack func, CFRunLoopObserverRef observer, CFRunLoopActivity activity, void *info) {
        if (func) {
            func(observer, activity, info);
        }
        getpid(); // thwart tail-call optimization
    }

I would love to know why this is seemingly so important, and are there any cases were I as a *normal* developer should keep this is mind too? Eg. are there common pitfalls with tail call optimization?

Why would code actively try to prevent tail-call optimization?

For example, if `somestruct` has three integer members, I had always thought that it was OK to do this in C (or C++) function:

    somestruct s = {123,};

The first member would be initialized to 123 and the last two would be initialized to 0. I often do the same thing with automatic arrays, writing `int arr[100] = {0,};` so that all integers in an array are initialized to zero. 

&lt;br&gt;
Recently I read in the [GNU C Reference Manual][1] that:

&gt; If you do not initialize a structure variable, the effect depends on
&gt; whether it is has static storage (see Storage Class Specifiers) or
&gt; not. If it is, members with integral types are initialized with 0 and
&gt; pointer members are initialized to NULL; otherwise, the value of the
&gt; structure&#39;s members is indeterminate.

&lt;br&gt;
Can someone please tell me what the C and C++ standards say regarding partial automatic structure and automatic array initialization? I do the above code in Visual Studio without a problem but I want to be compatible with gcc/g++, and maybe other compilers as well. Thanks

  [1]: http://www.gnu.org/software/gnu-c-manual/gnu-c-manual.html#Initializing-Structure-Members

C and C++ : Partial initialization of automatic structure

Why does C&#39;s printf format string have both `%c` and `%s`?

I know that `%c` represents a single character and `%s` represents a null-terminated string of characters, but wouldn&#39;t the string representation alone be enough? 

Why does C&#39;s printf format string have both %c and %s?

I write this code to read 3 files, TM is the size of square matrix, LER the No. of rows of an array and from last value define a non-square matrix of (ler/2)*2

Then... the code read a file with some relations, all are numbers and are assign to C[ler].

Then ... C[ler] is assigned to B[ler/2][2].

Those coordinates, per row, in B[ler/2][2] are assign to a and b.

a and b are the row and the column of the matrix A[tm][tm] where to add 1.

My code crashes and I don&#39;t see what the error is.

When I try to compile it, the compiler **gcc -g -o MatSim MatSim.cpp** prompted:

    /usr/include/c++/4.6/iostream:75: undefined reference to `std::ios_base::Init::Init()&#39;
    /usr/include/c++/4.6/iostream:75: undefined reference to `std::ios_base::Init::~Init()&#39;
    collect2: ld returned 1 exit status

Also, when I try to compile it, the compiler **f77 -o MatSim MatSim.cpp** prompted:

    /tmp/cc6ewlkf.o: In function `__static_initialization_and_destruction_0(int, int)&#39;:
    MatSim.cpp:(.text+0x17ad4a): undefined reference to `std::ios_base::Init::Init()&#39;
    MatSim.cpp:(.text+0x17ad4f): undefined reference to `std::ios_base::Init::~Init()&#39;
    collect2: ld returned 1 exit status



**Solution**

The main problem was a library problem, Compile your code using:

     g++ -g -o MatSim MatSim.cpp -lstdc

Still not working?  Install libraries:

    sudo apt-get install g++-multilib





undefined reference to `std::ios_base::Init::Init()&#39;

I understand how to create a `struct` on the heap using `malloc`. Was looking for some documentation regarding creating a `struct` in C on the stack but all docs. seem to talk about struct creation on heap only. 

How to create a struct on the stack in C?

I&#39;ve encounter a following [statement by Richard Stallman][1]:

&gt; &#39;When you start a Lisp system, it enters a read-eval-print loop. Most other languages have nothing comparable to read, nothing comparable to eval, and nothing comparable to print. What gaping deficiencies! &#39;

Now, I did very little programming in Lisp, but I&#39;ve wrote considerable amount of code in Python and recently a little in Erlang. My impression was that these languages also offer read-eval-print loop, but Stallman disagrees (at least about Python):

&gt; &#39;I skimmed documentation of Python after people told me it was fundamentally similar to Lisp. My conclusion is that that is not so. When you start Lisp, it does &#39;read&#39;, &#39;eval&#39;, and &#39;print&#39;, all of which are missing in Python.&#39;

Is there really a fundamental technical difference between Lisp&#39;s and Python&#39;s read-eval-print loops? Can you give examples of things that Lisp REPL makes easy and that are difficult to do in Python?


  [1]: http://stallman.org/stallman-computing.html

How is Lisp&#39;s read-eval-print loop different than Python&#39;s?

What command opens Ruby&#39;s REPL?

In Python, you simply open `python` without any arguments.

What command opens Ruby&#39;s REPL?

I saw a reference to creating a &quot;REPL&quot;.  What is a REPL?

    var arDrone = require(&#39;ar-drone&#39;);
    var client  = arDrone.createClient();
    client.createRepl();


What is a &quot;REPL&quot; in javascript?

When debugging Python code at the interactive prompt (REPL), often I&#39;ll write some code which raises an exception, but I haven&#39;t wrapped it in a `try`/`except`, so once the error is raised, I&#39;ve forever lost the exception object.

Often the traceback and error message Python prints out isn&#39;t enough. For example, when fetching a URL, the server might return a 40x error, and you need the content of the response via `error.read()` ... but you haven&#39;t got the error object anymore. For example:

    &gt;&gt;&gt; import urllib2
    &gt;&gt;&gt; f = urllib2.urlopen(&#39;http://example.com/api/?foo=bad-query-string&#39;)
    Traceback (most recent call last):
      File &quot;&lt;stdin&gt;&quot;, line 1, in &lt;module&gt;
      ...
    urllib2.HTTPError: HTTP Error 400: Bad Request

Drat, what did the body of the response say? It probably had valuable error information in it...

I realize it&#39;s usually easy to re-run your code wrapped in a try/except, but that&#39;s not ideal. I also realize that in this specific case if I were using the `requests` library (which doesn&#39;t raise for HTTP errors), I wouldn&#39;t have this problem ... but I&#39;m really wondering if there&#39;s a more general way to get the last exception object at a Python prompt in these cases.


How to get the last exception object after an error is raised at a Python prompt?

I created this function in Python 2.7 with `ipython`:

    def _(v):
        return v

later if I call `_(somevalue)`, I get `_ = somevalue`.

    in[3]: _(3)
    out[3]: 3
    in[4]: print _
    out[4]: 3

The function has disappeared! If I call `_(4)` I get:

```none
TypeError: &#39;int&#39; object is not callable
```

Why? What&#39;s wrong with this function?


Content Type	Original Author	Original Content on Stackoverflow
Question	Surya	View Question on Stackoverflow
Solution 1 - C	snd	View Answer on Stackoverflow
Solution 2 - C	gcbenison	View Answer on Stackoverflow
Solution 3 - C	Niklas B.	View Answer on Stackoverflow

Is there a REPL for C programming?

C Problem Overview

C Solutions

Solution 1 - C

Solution 2 - C

Solution 3 - C

Rails - Validate on Create Only

What Exception subclasses are built into PHP?

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