In C# I could do this:
char[] a = new char[] {'a', 'a', 'a'};
But can I do something like that in C++? I tried:
char *a = new char [] {'a', 'a', 'a'};
But it doesn't compile.
6 Answers
This is a bug in the C++ spec (which doesn't let this simple construct to compile). You need to supply the size
char *a = new char [3] {'a', 'a', 'a'};
See http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_active.html#1469 . Note that if you parenthesize the type name it is a type-id and not a new-type-id and hence syntactically allows you to omit the size expression. So you may be able to find an implementation that allows you to say
char *a = new (char[]){'a', 'a', 'a'};
Althought it is clear that it wasn't the explicit intent that this is possible (and some rules in the new paragraphs can be interpreted to forbid it).
answered Feb 10, 2013 at 17:27
Johannes Schaub - litb
510k132 gold badges925 silver badges1.2k bronze badges
3 Comments
Inverse
I don't think
new should be used here at all. Use the stack or a container.Johannes Schaub - litb
@inverse you should add that to the question as a comment. i do not recommend anything in my answer. i just fixed his syntax.
Johannes Schaub - litb
all the replies that talk about stack arrays or vectors do not really answer his question about the syntax of new.
why not just do this? :
char a[] = {'a', 'a', 'a'};
Also avoid using arrays completely. Use std::vector
2 Comments
Anton Kovalenko
It would be great to add something on initializers for
std::vector, like "if you're lucky enough to have a compiler supporting c++11, then you can so and so."
Aniket Inge
@AntonKovalenko I am not current on C++11, my focus has shifted to C#. But I would not mind if you want to add something to the answer :-)
You probably don't want to use an array in C++. Use a std::vector instead.
You can even initialise it to 3 'a's.
std::vector<char> vectorOfChars(3, 'a');
If your compiler supports C++11, you can even use an initialiser list.
std::vector<char> vectorOfChars{'a', 'a', 'a'};
Comments
I think what you want is this:
const char a[] = {'a', 'a', 'a'};
Comments
Comments
string a = "aaa"; a[0] , a[1] ..etc This will be much easier if you wanna make 2-D arrays of string..etc
char a[] = {'a', 'a', 'a'};. Much easier!char *a = new char [3] {'a', 'a', 'a'};