Initialize array in constructor's initialization list

Question

I'm trying to initialize an array in my constructor's intialization list, and I want the array to have the size MAX_SIZE, which is a public static const in my Stack class. How can I get it to work? The compiler complains, saying they have incompatible types in assignment of 'double' to 'double[0u]'

Here is my code:

class Stack {
    public:      
          Stack();
          static const unsigned MAX_SIZE; 
    private:
          double array[];
          unsigned elements;     
    };  // class Stack

    Stack::Stack(): array( array[MAX_SIZE] ), elements(0) {}

    const unsigned Stack::MAX_SIZE = 4;

Thanks in advance for your help.

Unless you're completely masochistic: static const unsigned max_size = 4; std::vector<double> array; Stack::Stack() : array(MAX_SIZE){} — Jerry Coffin
– Jerry Coffin, Commented Jun 4, 2012 at 0:21
Is there a simpler way perhaps? i.e. without using vectors. How can I get the program to accept my array data member with its size being MAX_SIZE? — Sean
– Sean, Commented Jun 4, 2012 at 0:30
I would get used to using std::vector. I rarely use arrays; I'll use a std::vector be preference nearly every time. The code @Jesse Good has given should work as well. — Jerry Coffin
– Jerry Coffin, Commented Jun 4, 2012 at 0:44
There are valid reasons to avoid vector. Vector always initializes on a heap while an array can be initialized over stack. — Anupam Srivastava
– Anupam Srivastava, Commented Apr 7, 2014 at 10:54

Jesse Good · Accepted Answer · 2012-06-04 00:32:40Z

5

 class Stack {
        public:
              Stack();
              static const unsigned MAX_SIZE = 4;
        private:
              double array[MAX_SIZE];
              unsigned elements;
        };  // class Stack

 Stack::Stack():  array(), elements(0) {}

But, std::vector would be better as mentioned in the comments.

answered Jun 4, 2012 at 0:32

Jesse Good

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9 Comments

Sean Over a year ago

I see.. so, basically, avoid initializing the array in the initialization list. Not possible, correct? Also, is it not possible to write my MAX_SIZE constant after main the way I did?

Sean Over a year ago

Reason I ask is cause I read differently on here, that the definition should be outside of the class: publib.boulder.ibm.com/infocenter/comphelp/v8v101/…

Jesse Good Over a year ago

array() in the intializer list zero initializes all the elements. You are correct, and I didn't define MAX_SIZE because I am only using it's value in the code. Define MAX_SIZE outside the class if you need to use it elsewhere.

Jerry Coffin Over a year ago

@Sean: You don't need a separate definition for a static const <integer type> variable like you do in other cases.

Jesse Good Over a year ago

@mezhaka: Yes, this form is called value initialization.

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