`std::get` returns a reference to the value. So you set the value like this:

    std::get&lt;0&gt;(myTuple) = newValue;

This of course assumes that `myTuple` is non-const. You can even move items out of a tuple via `std::move`, by invoking it on the tuple:

    auto movedTo = std::get&lt;0&gt;(std::move(myTuple));

The non-const version of `get` [returns a reference][1]. You can assign to the reference. For example, suppose `t` is tuple, then: `get&lt;0&gt;(t) = 3;`


  [1]: http://en.cppreference.com/w/cpp/utility/tuple/get

    map :: (a -&gt; b) -&gt; [a] -&gt; [b]

    fmap :: Functor f =&gt; (a -&gt; b) -&gt; f a -&gt; f b

    liftM :: Monad m =&gt; (a -&gt; b) -&gt; m a -&gt; m b

Why do we have three different functions that do essentially the same thing?

Why do we have map, fmap and liftM?

Every time I enter in a new player in the Admin portion of Django I get an error message that says &quot;This field is required.&quot;. 

Is there a way to make a field not required without having to create a custom form? Can I do this within models.py or admin.py?

Here&#39;s what my class in models.py looks like.
    
    class PlayerStat(models.Model):
        player = models.ForeignKey(Player)
        
        rushing_attempts = models.CharField(
            max_length = 100,
            verbose_name = &quot;Rushing Attempts&quot;
            )
        rushing_yards = models.CharField(
            max_length = 100,
            verbose_name = &quot;Rushing Yards&quot;
            )
        rushing_touchdowns = models.CharField(
            max_length = 100,
            verbose_name = &quot;Rushing Touchdowns&quot;
            )
        passing_attempts = models.CharField(
            max_length = 100,
            verbose_name = &quot;Passing Attempts&quot;
            )

Thanks 


Can I make an admin field not required in Django without creating a form?

One can get an element from `std::tuple` by index using `std::get`.
Analogically, how to *set* tuple&#39;s element by index?

How to set std::tuple element by index?

<p>One can get an element from <code>std::tuple</code> by index using <code>std::get</code>.
Analogically, how to <em>set</em> tuple's element by index?</p>


Apparently, we can pass complex class instances to functions, but why can&#39;t we pass arrays to functions?

Why can&#39;t we pass arrays to function by value?

As I&#39;ve learned recently, a `long` in C/C++ is the same length as an `int`.  To put it simply, why?  It seems almost pointless to even include the datatype in the language.  Does it have any uses specific to it that an `int` doesn&#39;t have?  I know we can declare a 64-bit `int` like so:

    long long x = 0;

But why does the language choose to do it this way, rather than just making a `long` well...longer than an `int`?  Other languages such as C# do this, so why not C/C++?

Long Vs. Int C/C++ - What&#39;s The Point?

I&#39;m curious about this code:

    cout &lt;&lt; &#39;test&#39;; // Note the single quotes.

gives me an output of `1952805748`. 

My question: Is the output an address in memory or something?

What do single quotes do in C++ when used on multiple characters?

I am using CMake on a small C++ project and so far it works great... with one twist :x

When I change a header file, it typically requires recompiling a number of sources files (those which include it, directly or indirectly), however it seems that cmake only detects *some* of the source files to be recompiled, leading to a corrupted state. I can work around this by wiping out the project and rebuilding from scratch, but this circumvents the goal of using a make utility: only recompiling what is needed.

Therefore, I suppose I am doing something wrong.

My project is very simply organized:

 - a top directory where all resources sit, the main CMakeLists.txt sits there
 - a &quot;include&quot; directory where all public headers lies (in various subdirectories)
 - a &quot;src&quot; directory where all the subdirectories for sources files are, the src CMakeLists.txt sits there
 - a CMakeLists.txt per subdirectory in the &quot;src&quot; directory

The main directory has:

    cmake_minimum_required(VERSION 2.8)
    
    project(FOO)
    
    set(EXECUTABLE_OUTPUT_PATH ${CMAKE_BINARY_DIR}/bin)
    
    # Compiler Options
    set(CMAKE_CXX_FLAGS &quot;${CMAKE_CXX_FLAGS} -g -std=c++0x -Wall -Wextra -Werror&quot;)
    
    include_directories($(FOO_SOURCE_DIR)/include)
    
    add_subdirectory(src)

The &quot;src&quot; directory:

    add_subdirectory(sub1)
    add_subdirectory(sub2)
    add_subdirectory(sub3)
    add_subdirectory(sub4)
    
    add_executable(foo main.cpp)
    
    target_link_libraries(foo sub1 sub2 sub3 sub4)

Where `sub4` depends on `sub3` which depends on `sub2` which depends on `sub1`

And an example of a subdirectory (sub3):

    set(SUB3_SRCS
        File1.cpp
        File2.cpp
        File3.cpp
        File4.cpp
        File5.cpp
        File6.cpp
        )
    
    add_library(sub3 ${SUB3_SRCS})
    
    target_link_libraries(sub3 sub1 sub2)

I&#39;d be glad if anyone could point my mistake to me, searching here or on CMake didn&#39;t yield anything so I guess it&#39;s very easy or should work out of the box...

(for reference, I am using cmake version 2.8.2 on MSYS)

**EDIT**:

Thanks to Bill&#39;s suggestion I have checked the `depend.make` file generated by CMake, and it is indeed lacking (severely). Here is an example:

    src/sub3/CMakeFiles/sub3.dir/File1.cpp.obj: ../src/sub3/File1.cpp

Yep, that&#39;s all, none of the includes were referenced at all :x


Handling header files dependencies with cmake

I was trying to create a vector of lambda, but failed:

    auto ignore = [&amp;]() { return 10; };  //1
    std::vector&lt;decltype(ignore)&gt; v;     //2
    v.push_back([&amp;]() { return 100; });  //3

Up to line #2,  it [compiles fine][1]. But the line#3 gives [compilation error][2]:

&gt;error: no matching function for call to &#39;std::vector&amp;lt;main()::&amp;lt;lambda()&gt;&gt;::push_back(main()::&amp;lt;lambda()&gt;)&#39;

I don&#39;t want a vector  of function pointers or vector of function objects. However, vector of function objects which encapsulate *real* lambda expressions, would work for me. Is this possible?

[1]:http://ideone.com/GYEDX
[2]:http://ideone.com/ddyJy

Why can&#39;t I create a vector of lambdas (of the same type) in C++11?

In my web application, I have a user list in a table on the left, and a user detail pane on the right. When the admin clicks a user in the table, its details should be displayed on the right.

I have a UserListView and UserRowView on the left, and a UserDetailView on the right. Things kind of work, but I have a weird behavior. If I click some users on the left, then click delete on one of them, I get successive javascript confirm boxes for all users that have been displayed. 

It looks like event bindings of all previously displayed views have not been removed, which seems to be normal. I should not do a new UserDetailView every time on UserRowView? Should I maintain a view and change its reference model? Should I keep track of the current view and remove it before creating a new one? I&#39;m kind of lost and any idea will be welcome. Thank you !

Here is the code of the left view (row display, click event, right view creation)

	window.UserRowView = Backbone.View.extend({
		tagName : &quot;tr&quot;,
		events : {
			&quot;click&quot; : &quot;click&quot;,
		},
		render : function() {
			$(this.el).html(ich.bbViewUserTr(this.model.toJSON()));
			return this;
		},
		click : function() {
			var view = new UserDetailView({model:this.model})
			view.render()
		}
	})

And the code for right view (delete button)

	window.UserDetailView = Backbone.View.extend({
		el : $(&quot;#bbBoxUserDetail&quot;),
		events : {
			&quot;click .delete&quot; : &quot;deleteUser&quot;
		},
		initialize : function() {
			this.model.bind(&#39;destroy&#39;, function(){this.el.hide()}, this);
		},
		render : function() {
			this.el.html(ich.bbViewUserDetail(this.model.toJSON()));
			this.el.show();
		},
		deleteUser : function() {
			if (confirm(&quot;Really delete user &quot; + this.model.get(&quot;login&quot;) + &quot;?&quot;)) 
				this.model.destroy();
			return false;
		}
	})



Backbone.js : repopulate or recreate the view?

I have a few class constants in my entity class, e.g.:

    class Entity {
        const TYPE_PERSON = 0;
        const TYPE_COMPANY = 1;
    }

In normal PHP I often do `if($var == Entity::TYPE_PERSON)` and I would like to do this kind of stuff in Twig. Is it possible?

How to access class constants in Twig?

What does it mean that compiler is using two phase lookup in order to compile template class?

Two phase lookup - explanation needed

&gt; **Possible Duplicate:**  
&gt; [Officially, what is typename for?](https://stackoverflow.com/questions/1600936/officially-what-is-typename-for)  
&gt; [Where and why do I have to put the template and typename keywords?](https://stackoverflow.com/questions/610245/where-and-why-do-i-have-to-put-template-and-typename)

&lt;!-- End of automatically inserted text --&gt;

consider the code below:

    template&lt;class K&gt;
    class C {
        struct P {};
        vector&lt;P&gt; vec;
        void f();
    };
    
    template&lt;class K&gt; void C&lt;K&gt;::f() {
        typename vector&lt;P&gt;::iterator p = vec.begin();
    }

Why is the &quot;typename&quot; keyword necessary in this example?
Are there any other cases where &quot;typename&quot; must be specified?



When is the &quot;typename&quot; keyword necessary?

I&#39;m new to Mustache.

Many templating languages (e.g., **Django** / **Jinja**) will let you extend a &quot;parent&quot; template like so...

### base.html
    &lt;html&gt;&lt;head&gt;&lt;/head&gt;
        &lt;body&gt;
        {% block content %}{% endblock %}
        &lt;/body&gt;
    &lt;/html&gt;

### frontpage.html
    {% extends &quot;base.html&quot; %}
    {% block content %}&lt;h1&gt;Foobar!&lt;/h1&gt;{% endblock %}


### rendered frontpage.html
    &lt;html&gt;&lt;head&gt;&lt;/head&gt;
        &lt;body&gt;
        &lt;h1&gt;Foobar!&lt;/h1&gt;
        &lt;/body&gt;
    &lt;/html&gt;


I&#39;m aware of Mustache&#39;s *partials* (e.g., `{{&gt;content}}`), but those seem to be just *includes*.

Does template extension exist for Mustache? Or, failing that, is there at least some design pattern that effectively turns *includes* into template extension equivalents.

Can Mustache Templates do template extension?

Is it possible in R to say - I want all indices from position `i` to the end of vector/matrix?
Say I want a submatrix from 3rd column onwards. I currently only know this way:

    A = matrix(rep(1:8, each = 5), nrow = 5) # just generate some example matrix...
    
    A[,3:ncol(A)] # get submatrix from 3rd column onwards

But do I really need to write `ncol(A)`? Isn&#39;t there any elegant way how to say &quot;from the 3rd column onwards&quot;? Something like `A[,3:]`? (or `A[,3:...]`)?


Elegant indexing up to end of vector/matrix

I have array that i had to unset some indexes so now it looks like

    $myarray [0] a-&gt;1
             [1] a-7 b-&gt;3
             [3] a-8 b-&gt;6
             [4] a-3 b-&gt;2

as you can see [2] is missing all i need to do is reset indexes so they show [0]-[3].

PHP reindex array?

My lower level knowledge of SQL (Server 2008) is limited, and is now being challanged by our DBAs. Let me explain (I have mentioned obvious statements in the hope that I am right, but if you see something wrong, please tell me) the scenario:

We have a table which holds &#39;Court Orders&#39; for people. When I created the table, (Name: CourtOrder), I created it like:

    CREATE TABLE dbo.CourtOrder
    (
      CourtOrderID INT NOT NULL IDENTITY(1,1), (Primary Key)
      PersonId INT NOT NULL,
      + around 20 other fields of different types.
    )

I then applied a non-clustered index to the primary key (for efficiency). My reasons is that it is a unique field (primary key), and should be indexed, mainly for selection purposes, as we often `Select from table where primary key = ...`

I then applied a CLUSTERED index on PersonId. The reason was to group orders for a particular person physically, as the vast majority of work is getting orders for a person. So, `select from mytable where personId = ...`

I have been pulled up on this now. I have been told that we should put the clustered index on the primary key, and the normal index on the personId. That seems very strange to me. First off, why would you put a clustered index on a unique column? what is it clustering? Surely that&#39;s a waste of the clustered index? I&#39;d have believed a normal index would be used on a unique column. Also, clustering the index would mean we can&#39;t cluster a different column (One per table, right?).

The reasoning for me being told I have made a mistake is that they believe putting a clustered index on the PersonId would make inserts slow. For the 5% gain in speed of a select, we would be getting a 95% degradation in speed on inserts and updates. Is that correct and valid?

They say that because we cluster the personId, SQL Server has to rearrange data when ever we insert or make a change to the PersonId.

So then I have asked, why would SQL have the concept of a CLUSTERED INDEX, if it&#39;s so slow? Is it as slow as they&#39;re saying? How should I have setup my indexes to achieve optimum performance? I&#39;d have thought SELECT is used more than INSERT... but they say that we&#39;re having locking issues on INSERTS...

Hope someone can help me.

Clustered vs Non-Clustered

In software engineering we create indexes all the time (e.g., in databases) but I also hear a lot of people talk about inverted indices. Is there something fundamentally different between the two? They sound like the same thing.

What&#39;s the difference between an inverted index and a plain old index?

I have a numpy array that contains some image data. I would like to plot the &#39;profile&#39; of a transect drawn across the image. The simplest case is a profile running parallel to the edge of the image, so if the image array is `imdat`, then the profile at a selected point `(r,c)` is simply `imdat[r]` (horizontal) or `imdat[:,c]` (vertical).

Now, I want to take as input two points `(r1,c1)` and `(r2,c2)`, both lying inside `imdat`. I would like to plot the profile of the values along the line connecting these two points.

What is the best way to get values from a numpy array, along such a line? More generally, along a path/polygon?

I have used slicing and indexing before, but I can&#39;t seem to arrive at an elegant solution for such a where consecutive slice elements are not in the same row or column. Thanks for your help.

How to extract an arbitrary line of values from a numpy array?

I want to assign multiple variables in a single line in R. Is it possible to do something like this?

    values # initialize some vector of values
    (a, b) = values[c(2,4)] # assign a and b to values at 2 and 4 indices of &#39;values&#39;

Typically I want to assign about 5-6 variables in a single line, instead of having multiple lines. Is there an alternative?



Assign multiple new variables on LHS in a single line

&gt; **Possible Duplicate:**  
&gt; [A Transpose/Unzip Function in Python](https://stackoverflow.com/questions/19339/a-transpose-unzip-function-in-python)  

&lt;!-- End of automatically inserted text --&gt;

I have a list that looks like this:

    list = ((&#39;1&#39;,&#39;a&#39;),(&#39;2&#39;,&#39;b&#39;),(&#39;3&#39;,&#39;c&#39;),(&#39;4&#39;,&#39;d&#39;))

I want to separate the list in 2 lists. 

    list1 = (&#39;1&#39;,&#39;2&#39;,&#39;3&#39;,&#39;4&#39;)
    list2 = (&#39;a&#39;,&#39;b&#39;,&#39;c&#39;,&#39;d&#39;)

I can do it for example with:

    list1 = []
    list2 = []
    for i in list:
       list1.append(i[0])
       list2.append(i[1])

But I want to know if there is a more elegant solution.

Unpacking a list / tuple of pairs into two lists / tuples

Is there a way to use a Tuple class, but supply the names of the items in it?

For example:

    public Tuple&lt;int, int, int int&gt; GetOrderRelatedIds()

That returns the ids for OrderGroupId, OrderTypeId, OrderSubTypeId and OrderRequirementId.

It would be nice to let the users of my method know which is which.  (When you call the method, the results are result.Item1, result.Item2, result.Item3, result.Item4.  It is not clear which one is which.)

(I know I could just create a class to hold all these Ids, but it these Ids already have their own classes they live in and making a class for this one method&#39;s return value seems silly.)

Better naming in Tuple classes than &quot;Item1&quot;, &quot;Item2&quot;

Given a string that is a sequence of several values separated by a commma:

    mStr = &#39;A,B,C,D,E&#39; 

How do I convert the string to a list?

    mList = [&#39;A&#39;, &#39;B&#39;, &#39;C&#39;, &#39;D&#39;, &#39;E&#39;]

How to convert comma-delimited string to list in Python?

I have a list of tuples. Every tuple has 5 elements (corresponding to 5 database columns) and I&#39;d like to make a query

    select attribute1 from mylist where attribute2 = something

e.g.

    personAge = select age from mylist where person_id = 10

Is it possible to query the list of tuples in some way?

Content Type	Original Author	Original Content on Stackoverflow
Question	Behrouz.M	View Question on Stackoverflow
Solution 1 - C++	Nicol Bolas	View Answer on Stackoverflow
Solution 2 - C++	amit kumar	View Answer on Stackoverflow

How to set std::tuple element by index?

C++ Problem Overview

C++ Solutions

Solution 1 - C++

Solution 2 - C++

Can I make an admin field not required in Django without creating a form?

Why do we have map, fmap and liftM?

Attributions