error invalid array assignment c

C++ 数组分配错误 : invalid array assignment

标签 c++ c arrays

我不是 C++ 程序员，所以我需要一些有关数组的帮助。 我需要将一个字符数组分配给某个结构，例如

我得到 error: invalid array assignment

如果 mStr.message 和 hello 具有相同的数据类型，为什么它不起作用？

因为您不能分配给数组——它们不是可修改的左值。使用 strcpy:

正如 Kedar 已经指出的那样，您还写出了数组的末尾。

关于C++ 数组分配错误 : invalid array assignment，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/4118732/

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SyntaxError: invalid assignment left-hand side

The JavaScript exception "invalid assignment left-hand side" occurs when there was an unexpected assignment somewhere. It may be triggered when a single = sign was used instead of == or === .

SyntaxError or ReferenceError , depending on the syntax.

What went wrong?

There was an unexpected assignment somewhere. This might be due to a mismatch of an assignment operator and an equality operator , for example. While a single = sign assigns a value to a variable, the == or === operators compare a value.

Typical invalid assignments

In the if statement, you want to use an equality operator ( === ), and for the string concatenation, the plus ( + ) operator is needed.

Assignments producing ReferenceErrors

Invalid assignments don't always produce syntax errors. Sometimes the syntax is almost correct, but at runtime, the left hand side expression evaluates to a value instead of a reference , so the assignment is still invalid. Such errors occur later in execution, when the statement is actually executed.

Function calls, new calls, super() , and this are all values instead of references. If you want to use them on the left hand side, the assignment target needs to be a property of their produced values instead.

Note: In Firefox and Safari, the first example produces a ReferenceError in non-strict mode, and a SyntaxError in strict mode . Chrome throws a runtime ReferenceError for both strict and non-strict modes.

Using optional chaining as assignment target

Optional chaining is not a valid target of assignment.

Instead, you have to first guard the nullish case.

• Assignment operators
• Equality operators

ProgrammerAH

Programmer guide, tips and tutorial, c++ bug: [error] invalid array assignment.

C++BUG: [Error] invalid array assignment

1. Introduction2. The difference between the return value of memcpy() function prototype function header file and strcpy

1. Introduction

When using array to assign value to array, the above bug will appear. The general chestnut is as follows:

The purpose is to store the data in the structure array object SS [J], but this assignment will report an error.

2. memcpy()

Function prototype

The data of consecutive n bytes with SRC pointing address as the starting address is copied into the space with destination pointing address as the starting address.

Header file

The use of # include & lt; string. H & gt;;

Both # include & lt; CString & gt; and # include & lt; string. H & gt; can be used in C + +

Return value

Function returns a pointer to dest.

The difference from strcpy

1. Compared with strcpy, memcpy does not end when it encounters’ \ 0 ‘, but will copy n bytes. Therefore, we need to pay special attention to memory overflow. 2. Memcpy is used to copy memory. You can use it to copy objects of any data type, and you can specify the length of the data to be copied. Note that source and destination are not necessarily arrays, and any read-write space can be used; however, strcpy can only copy strings, and it ends copying when it encounters’ \ 0 ‘.

For 2D arrays

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Problem with arrays

I'n trying to make a sketch about a led matrix 8x8 with 2 74hc595 shift register, but i have a problem with one array. I have several arrays declared like this:

int M[8][8]= { {0, 1, 1, 1, 0, 1, 1, 1}, {0, 0, 1, 0, 0, 1, 1, 1}, {0, 1, 0, 1, 0, 1, 1, 1}, {0, 1, 0, 1, 0, 1, 1, 1}, {0, 1, 1, 1, 0, 1, 1, 1}, {0, 1, 1, 1, 0, 1, 1, 1}, {0, 1, 1, 1, 0, 1, 1, 1}, {0, 1, 1, 1, 0, 1, 1, 1} };

and i want to make other array like this: const int LETRAS=25; int frase[LETRAS][8][8]={W,W,WW,P,R,A,C,T,I,C,A,N,D,O,A,R,D,U,I,N,OO,C,O,M,SPACE};

but i have this error 200: error: invalid conversion from 'int (*)[8]' to 'int'

If i try this way

int frase[LETRAS][8][8]; frase[0]= M;

i have the follow error: 203: error: invalid array assignment

Does anybody can help me please?

First things first - if all you saving in each element is a 1 or a 0, that's a huge waste of memory. Make the elements "byte" or better still, pack the bits.

And post your code - use code tags.

You've got two dimensions to that array, but you're only specifying one. That may "work" but it will bite you later.

Your biggest problem is that you are trying to shove a letter in a hole meant for a number. You have an int data type and then try to put M in it.

Maybe you want the ascii representation of M, so you could use 'M'. I'm not real sure what you want to do so I'm not sure how you should change it. But what you've got now is just completely wrong on too many levels to list.

Re-reading it, it isn't just a waste of memory, unless you're running it on a Mega, it's almost certainly more memory than you've got. So, "byte" rather than "int", and then eventually, you'll be moving the whole lot into PROGMEM.

i want to store in an array 25 matrix 8x8, each matrix position is an integer, so i will have 25 matrix like M (with different digits), so my question is how can i make this?

i want to store in an array 25 matrix 8x8, each matrix position is an integer,

You probably can't. That would be 3200 bytes, which is more than exists on an Arduino.

If you want to have an array of references to bitmaps, suitable for displaying on dot-matrix displays, that usually comes out somewhat differently. Keeping with the basics you have now, You could do:

More typically, one would pack bits into a sort of font table, stick that in program memory, and index it more-or-less directly from character values:

undesrtood, thanks to all, i'll try this way

Related Topics

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• passing char from one char array to anot

  passing char from one char array to another

C++ array assign error: invalid array assignment

Because you can’t assign to arrays — they’re not modifiable l-values. Use strcpy:

And you’re also writing off the end of your array, as Kedar already pointed out.

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Dev solutions

Solutions for development problems, c – error: invalid operands to binary * (have 'int' and 'sdl_window *') when attempting to use sdl_createwindow.

As seen on this issue here I had a few errors while trying to create a window, which are now fixed with this code:

However, there’s a new error now:

replacing the last line by SDL_Window = SDL_CreateWindow("title", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, 720, 480, 0); doesen’t trigger an error anymore, but it does give me a warning:

Nontheless,when running the executable a window does appear, but then instantly crash, i’m not sure if this is intended or not since there’s nothing after interacting with the window, but a warning is probably not a good sign. I figured it might have something to do with pointers, but I am way too much of a beginner to understand what causes this.

>Solution :

The issue appears to be that your code declares the variable SDL_Window to be an int , when you are assigning it to the result of a function call that returns an SDL_Window * ( link to documentation for SDL_CreateWindow() ). To fix this issue, try changing this line:

Also I would recommend changing the name of the variable SDL_Window to something else, such as window . This is to avoid confusion between the type named SDL_Window and the variable named SDL_Window .

To prevent the window from instantly "crashing", try calling scanf() after calling SDL_CreateWindow() . After the window opens, enter a key in the terminal you ran your program from and then press the "enter" key to close it. Also, don’t forget to call SDL_Quit() to quit SDL at the end of your program to free your process’s resources and return 0 to signify that your program ran successfully.

Full example

You may find this tutorial series helpful for learning more about SDL2.

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