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23.7 — std::initializer_list

Consider a fixed array of integers in C++:

If we want to initialize this array with values, we can do so directly via the initializer list syntax:

This prints:

This also works for dynamically allocated arrays:

In the previous lesson, we introduced the concept of container classes, and showed an example of an IntArray class that holds an array of integers:

This code won’t compile, because the IntArray class doesn’t have a constructor that knows what to do with an initializer list. As a result, we’re left initializing our array elements individually:

That’s not so great.

Class initialization using std::initializer_list

When a compiler sees an initializer list, it automatically converts it into an object of type std::initializer_list. Therefore, if we create a constructor that takes a std::initializer_list parameter, we can create objects using the initializer list as an input.

std::initializer_list lives in the <initializer_list> header.

There are a few things to know about std::initializer_list. Much like std::array or std::vector, you have to tell std::initializer_list what type of data the list holds using angled brackets, unless you initialize the std::initializer_list right away. Therefore, you’ll almost never see a plain std::initializer_list. Instead, you’ll see something like std::initializer_list<int> or std::initializer_list<std::string> .

Second, std::initializer_list has a (misnamed) size() function which returns the number of elements in the list. This is useful when we need to know the length of the list passed in.

Third, std::initializer_list is often passed by value. Much like std::string_view, std::initializer_list is a view. Copying a std::initializer_list does not copy the elements in the list.

Let’s take a look at updating our IntArray class with a constructor that takes a std::initializer_list.

This produces the expected result:

It works! Now, let’s explore this in more detail.

Here’s our IntArray constructor that takes a std::initializer_list<int> .

On line 1: As noted above, we have to use angled brackets to denote what type of element we expect inside the list. In this case, because this is an IntArray, we’d expect the list to be filled with int. Note that we don’t pass the list by const reference. Much like std::string_view, std::initializer_list is very lightweight and copies tend to be cheaper than an indirection.

On line 2: We delegate allocating memory for the IntArray to the other constructor via a delegating constructor (to reduce redundant code). This other constructor needs to know the length of the array, so we pass it list.size(), which contains the number of elements in the list. Note that list.size() returns a size_t (which is unsigned) so we need to cast to a signed int here.

The body of the constructor is reserved for copying the elements from the list into our IntArray class. For some inexplicable reason, std::initializer_list does not provide access to the elements of the list via subscripting (operator[]). The omission has been noted many times to the standards committee and never addressed.

However, there are easy ways to work around the lack of subscripts. The easiest way is to use a for-each loop here. The ranged-based for loop steps through each element of the initialization list, and we can manually copy the elements into our internal array.

Another way is to use the begin() member function to get an iterator to the std::initializer_list . Because this iterator is a random-access iterator, the iterators can be indexed:

List initialization prefers list constructors over non-list constructors

Non-empty initializer lists will always favor a matching initializer_list constructor over other potentially matching constructors. Consider:

The a1 case uses direct initialization (which doesn’t consider list constructors), so this definition will call IntArray(int) , allocating an array of size 5.

The a2 case uses list initialization (which favors list constructors). Both IntArray(int) and IntArray(std::initializer_list<int>) are possible matches here, but since list constructors are favored, IntArray(std::initializer_list<int>) will be called, allocating an array of size 1 (with that element having value 5)

This is why our delegating constructor above uses direct initialization when delegating:

That ensures we delegate to the IntArray(int) version. If we had delegated using list initialization instead, the constructor would try to delegate to itself, which will cause a compile error.

The same happens to std::vector and other container classes that have both a list constructor and a constructor with a similar type of parameter

Key insight

List initialization favors matching list constructors over matching non-list constructors.

Best practice

When initializing a container that has a list constructor:

  • Use brace initialization when intending to call the list constructor (e.g. because your initializers are element values)
  • Use direct initialization when intending to call a non-list constructor (e.g. because your initializers are not element values).

Adding list constructors to an existing class is dangerous

Because list initialization favors list constructors, adding a list constructor to an existing class that did not previously have one can cause existing programs to silently change behavior.

Consider the following program:

Now let’s add a list constructor to this class:

Although we’ve made no other changes to the program, this program now prints:

Adding a list constructor to an existing class that did not have one may break existing programs.

Class assignment using std::initializer_list

You can also use std::initializer_list to assign new values to a class by overloading the assignment operator to take a std::initializer_list parameter. This works analogously to the above. We’ll show an example of how to do this in the quiz solution below.

Note that if you implement a constructor that takes a std::initializer_list, you should ensure you do at least one of the following:

  • Provide an overloaded list assignment operator
  • Provide a proper deep-copying copy assignment operator
  • Delete the copy assignment operator

Here’s why: consider the following class (which doesn’t have any of these things), along with a list assignment statement:

First, the compiler will note that an assignment function taking a std::initializer_list doesn’t exist. Next it will look for other assignment functions it could use, and discover the implicitly provided copy assignment operator. However, this function can only be used if it can convert the initializer list into an IntArray. Because { 1, 3, 5, 7, 9, 11 } is a std::initializer_list, the compiler will use the list constructor to convert the initializer list into a temporary IntArray. Then it will call the implicit assignment operator, which will shallow copy the temporary IntArray into our array object.

At this point, both the temporary IntArray’s m_data and array->m_data point to the same address (due to the shallow copy). You can already see where this is going.

At the end of the assignment statement, the temporary IntArray is destroyed. That calls the destructor, which deletes the temporary IntArray’s m_data. This leaves array->m_data as a dangling pointer. When you try to use array->m_data for any purpose (including when array goes out of scope and the destructor goes to delete m_data), you’ll get undefined behavior.

If you provide list construction, it’s a good idea to provide list assignment as well.

Implementing a constructor that takes a std::initializer_list parameter allows us to use list initialization with our custom classes. We can also use std::initializer_list to implement other functions that need to use an initializer list, such as an assignment operator.

Question #1

Using the IntArray class above, implement an overloaded assignment operator that takes an initializer list.

The following code should run:

This should print:

Show Solution

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14. operations on arrays.

  • Assigning Arrays and Initializer Lists

Arrays are variables containing many elements, but an array can also be seen as having a single, compound value. It is thus possible to assign one array to another array of the same type. For example:

The last statement will make the variable array2 have three elements, of values 3, 8, 2, in that order.

It is not allowed to assign an array to another if the types of elements do not match. For example:

Braces and their content that is used to set the initial value of an array are called an initializer list . An initializer list creates a compound value made up of given values. It is possible to use an initializer list to assign a new compound value to an entire array, like this:

The initializer lists have better rules for automatic conversion. They have been introduced to the language recently, so this time the automatic conversion rules are proper. As you can see, an array of doubles can be assigned a list of integers.

It is not possible to perform assignment of an initializer list to an array if it would lose some information, for example:

In this example, both the third and the final element of the initializer list are preventing this assignment from being allowed, as the array has elements only of type int .

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Initializer list class reference

std::initializer_list is a light container that holds objects from list initialization or braced initialization.

This section requires improvement. You can help by editing this doc page.

Technical details ​

An object of type std::initializer_list<T> is a lightweight proxy object that provides access to an array of objects of type const T .

A std::initializer_list<T> object is automatically constructed when:

  • A braced-init-list is used to list-initialize an object, where the corresponding constructor accepts an std::initializer_list<T> parameter
  • A braced-init-list is used as the right operand of assignment or as a function call argument, and the corresponding assignment operator/function accepts an std::initializer_list<T> parameter
  • A braced-init-list is bound to auto, including in a ranged for loop

Initializer lists may be implemented as a pair of pointers or pointer and length.

Copying a std::initializer_list does not copy the underlying objects.

The underlying array is a temporary array of type const T[N] , in which each element is copy-initialized (except that narrowing conversions are invalid) from the corresponding element of the original initializer list. The lifetime of the underlying array is the same as any other temporary object, except that initializing an initializer list object from the array extends the lifetime of the array exactly like binding a reference to a temporary (with the same exceptions, such as for initializing a non-static class member). The underlying array may be allocated in read-only memory.

The program is ill-formed

std :: initializer_list

Template parameters ​, type names ​, member functions ​, iterators ​, non-member functions ​, free function templates overloaded for std::initializer_list ​.

  • Technical details
  • Template parameters
  • Non-member functions
  • Free function templates overloaded for std::initializer_list
  • About Sada Tech

How to Use an Initializer List to Assign Values to an Array

Introduction

In the realm of C++ programming, initializer lists are a remarkable tool for efficiently assigning values to arrays. They are a concise and elegant way to initialize arrays, enabling programmers to specify the elements in a single line of code, streamlining the initialization process and enhancing code readability. This article delves into the myriad benefits of using initializer lists for array assignment, provides comprehensive insights into their syntax and usage, compares them to alternative assignment methods, troubleshoots common issues, and explores the performance implications of this versatile technique.

The Power of Assigning to an Array from an Initializer List

Arrays serve as indispensable tools for managing and manipulating data in programming, offering a structured means to store elements of the same data type in contiguous memory. While arrays can be initialized through various methods, leveraging initializer lists presents several compelling advantages:

  • Concise and Efficient Initialization: Perhaps the most apparent advantage of assigning values to an array from an initializer list is the concise and efficient initialization process. Instead of tediously assigning each element individually, initializer lists enable you to specify all elements of the array in a single line of code. This saves valuable time and reduces the amount of code that needs to be written, making your code more elegant and maintainable.
  • Ensured Proper Initialization: When utilizing an initializer list to assign values to an array, the compiler diligently checks that the number of elements in the list corresponds to the size of the array. This automated validation helps prevent errors that might occur if the array were not properly initialized. It acts as a safety net, ensuring that your code remains robust and reliable.
  • Enhanced Code Readability: An often-overlooked advantage of using initializer lists is the improvement in code readability. By employing this method, programmers can clearly visualize the elements being assigned to the array, fostering a deeper understanding of how the array is utilized. This enhanced clarity simplifies debugging and aids in maintaining code over time.

In summary, assigning to an array from an initializer list streamlines the initialization process, enhances code reliability, and makes your code more readable. These advantages collectively contribute to its status as a valuable tool in the C++ programmer’s arsenal.

How to Utilize an Initializer List for Array Assignment

Assigning values to an array using an initializer list is straightforward and efficient. Follow these steps to make the most of this technique:

  • Declare the Array: Begin by declaring the array, specifying its size in the declaration. This step is essential as the size of the array determines the number of values that can be assigned using the initializer list. cpp Copy code int myArray[ 5 ]; // Declare an array of five integers
  • Assign Values Using the Initializer List: After declaring the array, assign values to it using an initializer list. The values within the list will be assigned to the elements of the array in the order they appear. cpp Copy code int myArray[ 5 ] = { 1 , 2 , 3 , 4 , 5 }; // Assign values 1, 2, 3, 4, 5 to the elements of the array

This concise process allows you to initialize arrays swiftly and efficiently, eliminating the need for repetitive assignments.

Syntax Demystified: Assigning to an Array from an Initializer List

Understanding the syntax of assigning values to an array from an initializer list is crucial for error-free implementation. Here’s the syntax demystified:

For instance, if you intend to assign the values 1, 2, and 3 to an array named myArray , you would write:

It’s imperative to note that the number of values within the initializer list must precisely match the size of the array. If the list contains more values than the array can accommodate, the surplus values will be disregarded. Conversely, if the initializer list contains fewer values than the array’s size, the remaining elements will be initialized to their default values.

This straightforward syntax simplifies the assignment process and enhances code clarity, allowing programmers to express their intentions succinctly.

Initializer Lists vs. Other Array Assignment Methods

When it comes to assigning values to arrays, several methods are at your disposal. However, initializer lists stand out as an efficient and convenient choice. Let’s compare assigning to an array from an initializer list to alternative methods:

  • Initializer lists are particularly advantageous when the array size is known in advance, and the values are predetermined. In such cases, they enable you to assign values in a single line of code, offering a more efficient and elegant solution compared to looping through the array and assigning each element individually.
  • Loop-based assignment can be useful when you need to assign values to an array dynamically or based on certain conditions. It provides flexibility but may result in more verbose code and increased complexity.
  • Manual element assignment is the most basic method of assigning values to an array. While it provides complete control, it can be cumbersome and error-prone, especially for large arrays.
  • Initializer lists shine in terms of simplicity and readability, making it easier to express the array’s initial state succinctly.
  • Some programming languages provide functions or methods for array initialization. While these can be powerful, they often introduce additional overhead, making them less efficient than initializer lists.
  • Initializer lists are a direct and efficient means of initializing arrays, reducing unnecessary function call overhead.
  • One significant advantage of using initializer lists is type safety. The compiler automatically checks that the values in the list match the array’s data type. This prevents type-related errors that can occur when using other assignment methods.

In summary, initializer lists are a preferred choice for array assignment when the array size is known and the values are predetermined. They offer efficiency, readability, and type safety, making them a valuable asset in many programming scenarios.

Troubleshooting Common Issues with Initializer Lists for Array Assignment

While initializer lists are powerful, they are not immune to common issues. Here are some troubleshooting tips to address potential problems:

  • Size Mismatch: Ensure that the number of elements in the initializer list matches the size of the array. If they differ, the compiler will raise an error. To avoid this, always double-check the size when assigning values using initializer lists.
  • Type Mismatch: Verify that the data type of the elements in the initializer list matches the data type of the array. A type mismatch will result in a compilation error. Maintaining consistency in data types is essential for error-free array initialization.
  • Multidimensional Arrays: When dealing with multidimensional arrays, ensure that the nesting of the initializer list matches the array’s structure. Incorrect nesting will lead to compilation errors. Carefully align the structure of the initializer list with that of the array to avoid issues.

By paying attention to these common issues, you can harness the full potential of initializer lists for array assignment and minimize troubleshooting efforts.

Performance Considerations: Initializing Arrays with Initializer Lists

While initializer lists offer a convenient means of array initialization, it’s essential to consider their performance implications, particularly for large arrays. Initializing arrays with initializer lists involves copying each element from the list into the array, which can be time-consuming. Additionally, the compiler generates code to verify that the list’s size matches the array’s size, introducing further overhead.

To determine whether initializer lists are the right choice for your array initialization, consider the following factors:

  • Array Size: For small arrays, the performance impact of using initializer lists is negligible, and the benefits of concise and readable code often outweigh any performance concerns.
  • Large Arrays: When dealing with large arrays, the overhead introduced by copying elements from the initializer list can become noticeable. In such cases, alternative methods, such as loop-based initialization, may offer better performance.
  • Complex Initialization Logic: If the initialization process involves complex logic or calculations, initializer lists may not be the most efficient choice. Using a loop allows you to perform computations or apply conditional logic while initializing the array.
  • Compile-Time vs. Runtime: Keep in mind that initializer lists are resolved at compile time, which means the values assigned to the array must be known at compile time. If you require runtime determination of values, other methods like loop-based initialization or functions may be more suitable.

In conclusion, while initializer lists offer a convenient and elegant means of initializing arrays, their performance impact can vary depending on factors such as array size and complexity of initialization logic. It’s essential to strike a balance between code readability and performance when choosing the appropriate method for array initialization.

Assigning values to arrays from initializer lists is a potent technique in C++ programming, offering efficiency, reliability, and improved code readability. By embracing initializer lists, you can streamline the array initialization process, reduce the risk of errors, and make your code more maintainable.

This article has explored the myriad benefits of using initializer lists, explained the syntax and usage, compared them to alternative methods, addressed common issues, and considered the performance implications. Armed with this knowledge, you can make informed decisions about when and how to leverage initializer lists for array assignment, ensuring your code remains both elegant and efficient.

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When do we use Initializer List in C++?

Initializer List is used in initializing the data members of a class. The list of members to be initialized is indicated with constructor as a comma-separated list followed by a colon. Following is an example that uses the initializer list to initialize x and y of Point class.

The above code is just an example for syntax of the Initializer list. In the above code, x and y can also be easily initialed inside the constructor. But there are situations where initialization of data members inside constructor doesn’t work and Initializer List must be used. The following are such cases:

1. For Initialization of Non-Static const Data Members

const data members must be initialized using Initializer List. In the following example, “t” is a const data member of Test class and is initialized using Initializer List. Reason for initializing the const data member in the initializer list is because no memory is allocated separately for const data member, it is folded in the symbol table due to which we need to initialize it in the initializer list. 

Also, it is a Parameterized constructor and we don’t need to call the assignment operator which means we are avoiding one extra operation.

2. For Initialization of Reference Members

Reference members must be initialized using the Initializer List. In the following example, “t” is a reference member of the Test class and is initialized using the Initializer List.

3. For Initialization of Member Objects that do not have a Default Constructor

In the following example, an object “a” of class “A” is a data member of class “B”, and “A” doesn’t have a default constructor. Initializer List must be used to initialize “a”.

If class A had both default and parameterized constructors, then Initializer List is not a must if we want to initialize “a” using the default constructor, but it is must to initialize “a” using the parameterized constructor. 

4. For Initialization of Base Class Members

Like point 3, the parameterized constructor of the base class can only be called using the Initializer List.

5. When the Constructor’s Parameter Name is the Same as Data Member

If the constructor’s parameter name is the same as the data member name then the data member must be initialized either using this pointer or Initializer List. In the following example, both the member name and parameter name for A() is “i”.

6. For Performance Reasons

It is better to initialize all class variables in the Initializer List instead of assigning values inside the body. Consider the following example:

Here compiler follows following steps to create an object of type MyClass 

1. Type’s constructor is called first for “a”. 

2. Default construct “variable”

3. The assignment operator of “Type” is called inside body of MyClass() constructor to assign 

4. And then finally destructor of “Type” is called for “a” since it goes out of scope.

Now consider the same code with MyClass() constructor with Initializer List

With the Initializer List, the following steps are followed by compiler: 

1. Type’s constructor is called first for “a”.  2. Parameterized constructor of “Type” class is called to initialize: variable(a). The arguments in the initializer list are used to copy construct “variable” directly.  3. The destructor of “Type” is called for “a” since it goes out of scope.

As we can see from this example if we use assignment inside constructor body there are three function calls: constructor + destructor + one addition assignment operator call. And if we use Initializer List there are only two function calls: copy constructor + destructor call. See this post for a running example on this point.

This assignment penalty will be much more in “real” applications where there will be many such variables. Thanks to ptr for adding this point. 

Parameter vs Uniform Initialization in C++

It is better to use an initialization list with uniform initialization {} rather than parameter initialization () to avoid the issue of narrowing conversions and unexpected behavior. It provides stricter type-checking during initialization and prevents potential narrowing conversions

Code using parameter initialization () 

In the above code, the value 300 is out of the valid range for char, which may lead to undefined behavior and potentially incorrect results. The compiler might generate a warning or error for this situation, depending on the compilation settings.

Code using uniform initialization {}

By using uniform initialization with {} and initializing x with the provided value a, the compiler will perform stricter type-checking and issue a warning or error during compilation, indicating the narrowing conversion from int to char. Here is code with uniform initialization {} , which results in a warning and thus better to use

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Std::vector<t,allocator>:: assign.

Replaces the contents of the container.

All iterators, pointers and references to the elements of the container are invalidated. The past-the-end iterator is also invalidated.

[ edit ] Parameters

[ edit ] complexity, [ edit ] example.

The following code uses assign to add several characters to a std:: vector < char > :

[ edit ] See also

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  • Error:assigning to an array from an init

  Error:assigning to an array from an initializer list

assigning to array from initializer list

assigning to an array from an initializer list (after a ubuntu change version)

What is the point of piggybacking onto a 2-month old thread, if you don't read the previous replies, and get information from them?

@hashimashraf - what you have is not valid C++. You need to read a tutorial, and learn some of the basics of the language.

Thanks all its Working NOW Regards Hashim Ashraf -(* _ * )-

If you're referring to me I didn't realize it was as it was at the top of the current posting when I replied!

lloyddean: If you're referring to me I didn't realize it was as it was at the top of the current posting when I replied!

:wink:

I was referring to the post by hashimashraf which was made two months after the last post in this thread. The one not in code tags.

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COMMENTS

  1. How can I assign an array from an initializer list?

    How can I assign an array from an initializer list? Ask Question Asked 8 years, 9 months ago Modified 2 years, 2 months ago Viewed 83k times 23 I have a limited knowledge about c++. I tried to compile a c++ library and when I run the make file for the following header file mcmc_dhs.h #include <algorithm> #include <map>

  2. std::initializer_list

    An object of type std::initializer_list<T> is a lightweight proxy object that provides access to an array of objects of type const T (that may be allocated in read-only memory). A std::initializer_list object is automatically constructed when:

  3. List-initialization (since C++11)

    List initialization is performed in the following situations: direct-list-initialization (both explicit and non-explicit constructors are considered) initialization of an unnamed temporary with a initialization of an object with dynamic storage duration with a , where the initializer is a

  4. 23.7

    If we want to initialize this array with values, we can do so directly via the initializer list syntax: #include <iostream> int main() { int array [] { 5, 4, 3, 2, 1 }; // initializer list for (auto i : array) std :: cout << i << ' '; return 0; } This prints: 5 4 3 2 1 This also works for dynamically allocated arrays:

  5. Assigning Arrays and Initializer Lists

    It is possible to use an initializer list to assign a new compound value to an entire array, like this: arrayDouble = {9, 10, 11, 12, 13}; The initializer lists have better rules for automatic conversion. They have been introduced to the language recently, so this time the automatic conversion rules are proper.

  6. std::initializer_list reference

    Overview template< class T > class initializer_list; std::initializer_list is a light container that holds objects from list initialization or braced initialization. Memory info This section requires improvement. You can help by editing this doc page. Technical details Feature testing macros Technical definition std :: initializer_list Defined in

  7. Array initialization

    When initializing an object of array type, the initializer must be either a string literal (optionally enclosed in braces) or be a brace-enclosed list of initialized for array members: string-literal ={expression,...} (until C99) ={designator(optional)expression,...} (since C99) } (since C23)

  8. Initializing Arrays in Java

    Discover different ways of initializing arrays in Java. The java.util.Arrays class has several methods named fill(), which accept different types of arguments and fill the whole array with the same value:. long array[] = new long[5]; Arrays.fill(array, 30); The method also has several alternatives, which set the range of an array to a particular value:

  9. Is it possible to assign to an array from an initializer list?

    1 Doesn't matter which version of C++ you use. An array is not assignable. You can initialise it in the definition (i.e. int arrayname_A [] = {1,2,3,4,5}; which is not an assignment) and subsequently manipulate elements individually (e.g. in a loop) but not assign the whole array.

  10. How to Use an Initializer List to Assign Values to an Array

    Assigning values to an array using an initializer list is straightforward and efficient. Follow these steps to make the most of this technique: Declare the Array: Begin by declaring the array, specifying its size in the declaration.

  11. assigning to an array from an initializer list (after a ubuntu change

    assigning to an array from an initializer list (after a ubuntu change version) Using Arduino system November 21, 2013, 10:13am 1 Hello guys, A very strange problem. I had a 12.04 ubuntu, Arduino V1.0 and this code worked perfectly : int chaine [2]; void setup () { chaine= {1,2}; } void loop () {}

  12. When do we use Initializer List in C++?

    With the Initializer List, the following steps are followed by compiler: 1. Type's constructor is called first for "a". 2. Parameterized constructor of "Type" class is called to initialize: variable(a). The arguments in the initializer list are used to copy construct "variable" directly. 3.

  13. Assigning to an array from an initializer list

    Error - Assigning to an array from an initializer list anon90086852 October 11, 2022, 4:13am 1 Hi, My code is stuck at this error, how to rectify? It isn't accepting lastchancename October 11, 2022, 4:27am 2 Can you post the complete error message as shown in the IDE .? GolamMostafa October 11, 2022, 4:35am 4 anon90086852: volume = {'0', '0', '0'};

  14. C++ assigning to an array from an initializer list

    -1 I have been working on a program to display a menu to the screen. It was working but void parser() { parsed[0]=data[position]; for (i=1; i<=Choices; i++) { for (ii = 0; ii<= Depth-cDepth; ii++) { incriment += pow(Choices, ii); } incriment++; buff = position + incriment; parsed[i] = data[buff]; } cout << parsed; }

  15. std::vector<T,Allocator>::assign

    3) Replaces the contents with the elements from the initializer list ilist. All iterators, pointers and references to the elements of the container are invalidated. The past-the-end iterator is also invalidated.

  16. Error:assigning to an array from an initializer list

    1 2 unsigned int xor_result_arr [4] = {0}; unsigned int trans_val_1 [4] = {xor_result_arr [0], xor_result_arr [1], xor_result_arr [2], xor_result_arr [3]}; Jan 28, 2014 at 4:09am amitk3553 (102) Yes, but there is an error: Error:assigning to an array from an initializer list Jan 28, 2014 at 4:21am Peter87 (11126)

  17. C++ : How can I assign an array from an initializer list?

    C++ : How can I assign an array from an initializer list?To Access My Live Chat Page, On Google, Search for "hows tech developer connect"As promised, I have ...

  18. How do I initialize a member array with an initializer_list?

    8 Answers Sorted by: 72 You can use a variadic template constructor instead of an initializer list constructor: struct foo { int x [2]; template <typename...

  19. error:assigning to an array from an initializer list c++

    1 Answer Sorted by: 1 You can't assign to an array, only copy to it. One possible solution here is to make another array, say e.g. new_passw that you initialize: int new_passw[8][2] = {{b[0]+1,b[1]+2}, ... }}; Then you copy from this new_passw array into the old passw array. Share Improve this answer Follow answered Jan 23, 2020 at 8:07

  20. Assigning to an Array from an Initializer List Question

    int values [] = {1,2,3}; is the standard way of doing it. Your last way doesn't work because you're calling the array initializer twice which is not allowed. •. So short answer is: int values [] = {1,2,3}; is an initializer format. But you can see what the coder is trying to accomplish. Is there actually a way to assign values in the single ...

  21. assigning to an array from an initializer list (after a ubuntu change

    assigning to an array from an initializer list (after a ubuntu change version) Using Arduino. Programming Questions. ... "Compilation error: assigning to an array from an initializer list" When changing values of an array. Programming Questions. 12: 420: October 2, 2023 Array question. Syntax & Programs. 11: