How to initialize a large private array in a class using constructor(just a constructor) in c++? [duplicate]

Question

Suppose we have a class like the following one:

class myprogram {
public:
myprogram ();
private:
double aa,bb,cc;};
myprogram::myprogram():aa(0.0),bb(0.0),cc(0.0){}

As you can see we can initialize our private members' aa, bb, cc using the myprogram() constructor.

Now, suppose I have a large private array G_[2000]. how I could initialize all the values of this array equal to 0 using a constructor.

class myprogram {
public:
myprogram ();
private:
double aa,bb,cc;
double G_[2000];};
myprogram::myprogram():aa(0.0),bb(0.0),cc(0.0){}

@sshashank124 No. I want to use it in a class and using a constructor. — Seyyed Kazem Razavi
– Seyyed Kazem Razavi, Commented Jan 14, 2020 at 7:55
Does this answer your question? Zero-Initialize array member in initialization list — Daniel Langr
– Daniel Langr, Commented Jan 14, 2020 at 7:58
I have added a new answer in the duplicate question that specificatlly addresses this one i(initialization to 0 or 0.). — Serge Ballesta
– Serge Ballesta, Commented Jan 14, 2020 at 8:26
@SergeBallesta I have tried the approach you introduced, but it does not work. — Seyyed Kazem Razavi
– Seyyed Kazem Razavi, Commented Jan 14, 2020 at 8:41
it does not work just means nothing. You'd better ask a new question refering this one and my answer if it helps and explaining what you have tried, the expected result and the actual result. Be sure to read (again?) How to Ask to make it a nice question... — Serge Ballesta
– Serge Ballesta, Commented Jan 14, 2020 at 9:06

Ladence · Accepted Answer · 2020-01-14 08:50:14Z

1

Use std::memset function in constructor's body.

For example,

myprogram::myprogram()
     : aa{0.0}, bb{0.0}, cc{0.0}
{
    std::memset(G_, 0, 2000 * sizeof(double));
}

However, if you use braces {} in your initializer list, it will set default-initialize object (In case of array, it will fill it by zeroes).

answered Jan 14, 2020 at 8:03

Ladence

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1 Comment

don't forget #include <cstring>

Domenico Lanza · Accepted Answer · 2020-01-14 08:01:03Z

0

You can write:

    myprogram::myprogram()
    {
          for(int i=0;i<2000;i++)
             G_[i]=0;
    }

answered Jan 14, 2020 at 8:01

Domenico Lanza

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Tnx. I think it could works

If you have resolved please accept and up my question