How to declare an array and then assign in another line

Question

class c{};

c *ar[2];

ar = {new c, new c}; //error

"Array type is not assignable" How to assign it after declaring it, i want to do that because the class is using that variable so i just want to declare it, create a class and then assign the value, i can't assign before the class because it can't make a new c without defing the class first.

You can't *assign* to an array, only copy to it or set its element separately. — Some programmer dude, Jul 20 '17 at 12:15
Read the last part of my comment again... Or use [`std::array`](http://en.cppreference.com/w/cpp/container/array) instead. — Some programmer dude, Jul 20 '17 at 12:18
i have 64 elements to set, should i set them seperately or use std::array? what does the std::array do — Viktor Lazic, Jul 20 '17 at 12:22
@ViktorLazic I would suggest you to study a good c++ book. SO is not here to baby spoon everyone. Google is your friend. — KostasRim, Jul 20 '17 at 12:25
Sounds like you could benefit from reading one of [these C++ books](https://stackoverflow.com/questions/388242/the-definitive-c-book-guide-and-list). — Ron, Jul 20 '17 at 12:38
If the class `c` is using the array, that's probably part of the reason you're stuck. (Also see [What is the XY problem?](https://meta.stackexchange.com/questions/66377/what-is-the-xy-problem) — molbdnilo, Jul 20 '17 at 12:41

Andriy Tylychko · Answer 1 · 2017-07-20T13:06:21.210

1

use standard library algorithm generate:

#include <algorithm>
#include <iterator>

class c{};
c* ar[2];
std::generate(std::begin(ar), std::end(ar), [] { return new c; });

edited Jul 20 '17 at 13:06

answered Jul 20 '17 at 12:46

Andriy Tylychko

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What was wrong with your previous version using `std::begin` and `std::end`? It's more readable (from begin to end), and less error prone – KABoissonneault Jul 20 '17 at 12:59
@KABoissonneault: https://godbolt.org/g/SFeaBh, GCC 7.1 failed, same `error: no matching function for call to 'begin(c* [2])'` with Clang 4.0, works fine with VS2015 or GCC 4.9, surprised, investigating – Andriy Tylychko Jul 20 '17 at 13:01
2

Try including `` – KABoissonneault Jul 20 '17 at 13:04

score 0 · Answer 2 · answered Jul 20 '17 at 12:28

0

use a loop:

for(auto i = std::begin(ar);i!=std::end(ar);++i)
    *i = new c;

this will work for (almost) all container classes, not just raw arrays.

answered Jul 20 '17 at 12:28

IlBeldus

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How to declare an array and then assign in another line

2 Answers2