re-initializing an array

[heights]

Hi

Please have a look on the embedded questions in the code below. Thank you for all the help.

// learning initialization.cpp

#include <iostream>
#include <cstdlib>
#include <cstring>

using namespace std;

const int C = 20;

int main()
{
        char name[C] = {0}; // 10 zeroes
        int v = 10;

        cout << v << endl;

        v = 20;

        cout << v << endl;
        cout << name << endl;

        name[C] = {2} /* is this possible to re-initialize an array this way? one two and 9 zeroes */

        system("pause");
        return 0;
}

[Paul McKenzie]

name[C] = {2} /* is this possible to re-initialize an array this way? one two and 9 zeroes */

No.

The term initialization has a specific meaning in C++. Nothing in C++ can be initialized more than once. Once something is initialized, it can only be changed using assignment.

Regards,

Paul McKenzie

[Lindley]

If you want you can use scoping rules to make one version of the variable go out of scope, and then bring another one in:

#include <iostream>
#include <cstdlib>
#include <cstring>

using namespace std;

const int C = 20;

int main()
{
    {
        char name[C] = {0}; // 10 zeroes
        int v = 10;

        cout << v << endl;

        v = 20;

        cout << v << endl;
        cout << name << endl;
    }
    {
        char name[C] = {2};

        system("pause");
        return 0;
    }
}

Note these are completely separate arrays which just happen to have the same name.

[Philip Nicoletti]

char name[C] = {0}; // 10 zeroes

//

name[C] = {2} /* is this possible to re-initialize an array this way? one two and 9 zeroes */

1. The second statement is only legal in C++0x

2. The way that I read the standard ... the second statement is the same as :

name[C] = char(2);

(which is out of bounds of the array).

[vkash]

Hi

Please have a look on the embedded questions in the code below. Thank you for all the help.

// learning initialization.cpp

#include <iostream>
#include <cstdlib>
#include <cstring>

using namespace std;

const int C = 20;

int main()
{
        char name[C] = {0}; // 10 zeroes
        int v = 10;

        cout << v << endl;

        v = 20;

        cout << v << endl;
        cout << name << endl;

        name[C] = {2} /* is this possible to re-initialize an array this way? one two and 9 zeroes */

        system("pause");
        return 0;
}

It has many 3 errors

Compiling...
main.cpp
..............cpp(22) : error C2059: syntax error : '{'
..............cpp(22) : error C2143: syntax error : missing ';' before '{'
..............cpp(22) : error C2143: syntax error : missing ';' before '}'

in line

name[C] = {2} /* is this possible to re-initialize an array this way? one two and 9 zeroes */

you are trying to access 20th data of name array but is that exist. NO. Your program may crach in such condition.
I like the answer of paul he says about initialization meaning.

The term initialization has a specific meaning in C++. Nothing in C++ can be initialized more than once. Once something is initialized, it can only be changed using assignment.

heights you are understanding wrong meaning of initialization.
If you want to change all the data in array to 2 then try this code

// learning initialization.cpp

#include <iostream>
#include <cstdlib>
#include <cstring>

using namespace std;

const int C = 20;

int main()
{
        char name[C] = {0}; // 10 zeroes
        int v = 10;

        cout << v << endl;

        v = 20;

        cout << v << endl;
        cout << name << endl;

        for(int i=0;i<20;i++)
        name[i]='2';
        return 0;
}

one basic question to you in red region i put name[i]='2' not name[i]=2 why. what will change if i do so.

[D_Drmmr]

heights you are understanding wrong meaning of initialization.
If you want to change all the data in array to 2 then try this code

But what the OP understood correctly and you did not, is that the code

char name[10] = {2};

does not initialize the array with ten 2s.

[GCDEF]

It has many 3 errors

Compiling...
main.cpp
..............cpp(22) : error C2059: syntax error : '{'
..............cpp(22) : error C2143: syntax error : missing ';' before '{'
..............cpp(22) : error C2143: syntax error : missing ';' before '}'

in line

name[C] = {2} /* is this possible to re-initialize an array this way? one two and 9 zeroes */

you are trying to access 20th data of name array but is that exist. NO. Your program may crach in such condition.
I like the answer of paul he says about initialization meaning.


heights you are understanding wrong meaning of initialization.
If you want to change all the data in array to 2 then try this code

// learning initialization.cpp

#include <iostream>
#include <cstdlib>
#include <cstring>

using namespace std;

const int C = 20;

int main()
{
        char name[C] = {0}; // 10 zeroes
        int v = 10;

        cout << v << endl;

        v = 20;

        cout << v << endl;
        cout << name << endl;

        for(int i=0;i<20;i++)
        name[i]='2';
        return 0;
}

one basic question to you in red region i put name[i]='2' not name[i]=2 why. what will change if i do so.

It's great that you're trying to help, but by the questions you ask, I'm not sure you're ready. You may want to look at this table to find out the difference between the character 2 and the numeric value of 2.

http://www.asciitable.com/

Also, name[C] is the 21st element of name, not the 20th.

[vkash]

It's great that you're trying to help, but by the questions you ask, I'm not sure you're ready. You may want to look at this table to find out the difference between the character 2 and the numeric value of 2.

http://www.asciitable.com/

Also, name[C] is the 21st element of name, not the 20th.

GCDEF when i start my C++ i have learnt these things carefully and i know these things still now also.I ask his question to heights because i want to tell him are you perfect in this thing.
My answer to my own question is
when we write

 for(int i=0;i<20;i++)
        name[i]='2'

here name [i] is set to 2 but when we type

for(int i=0;i<20;i++)
        name[i]=2

here we are telling to set name[i] to that value whose number in ASCII standards is 2. there are 256 such characters. these characters repeat after 256(-128 to 128). I have got this info from my VC++ code that is

#include<iostream>
using namespace std;
int main()
{
	for(int i=-150;i<128;i++)
		cout<<i<<"  "<<char(i)<<endl;
	return 0;
}

you have good link but i had already got all those things.

you are trying to access 20th data of name array but is that exist

Also, name[C] is the 21st element of name, not the 20th.

heights i am sorry for wrong answer.
shiiiit i go here in bjarne stroustrup method of counting not general counting method. I don't know why bjarne stroustrup break convention to start counting from 0 rather than 1. there may be several reasons like first ten have single digit in such counting method.

[GCDEF]

GCDEF when i start my C++ i have learnt these things carefully and i know these things still now also.I ask his question to heights because i want to tell him are you perfect in this thing.
My answer to my own question is
when we write

 for(int i=0;i<20;i++)
        name[i]='2'

here name [i] is set to 2 but when we type

for(int i=0;i<20;i++)
        name[i]=2

here we are telling to set name[i] to that value whose number in ASCII standards is 2. there are 256 such characters. these characters repeat after 256(-128 to 128). I have got this info from my VC++ code that is

#include<iostream>
using namespace std;
int main()
{
	for(int i=-150;i<128;i++)
		cout<<i<<"  "<<char(i)<<endl;
	return 0;
}

you have good link but i had already got all those things.


heights i am sorry for wrong answer.
****i go here in bjarne stroustrup method of counting not general counting method. I don't know why bjarne stroustrup break convention to start counting from 0 rather than 1. there may be several reasons like first ten have single digit in such counting method.

Oh dear. We don't use profanity in this forum.

Stroustrup has nothing to do with array indexes beginning with 0. Think of the index as an offset from the start of the array, not an index number.

You still seem a little confused between the difference between the number 2 and the character 2.

[vkash]

Oh dear. We don't use profanity in this forum.

.

I have no intention of abusing(profanity) here.
I don't abuse in real life as well as in any public internet place like this this. I write this word here because i think it's meaning is different. now i know that it is profanity in modern English.

You still seem a little confused between the difference between the number 2 and the character 2

I don't thing i am confused between these number2 and character 2.
if you think so then explain it in your words. heights will also get benefit from from this.

[MrViggy]

My answer to my own question is
when we write

 for(int i=0;i<20;i++)
        name[i]='2'

here name [i] is set to 2 but when we type

for(int i=0;i<20;i++)
        name[i]=2

here we are telling to set name[i] to that value whose number in ASCII standards is 2. there are 256 such characters. these characters repeat after 256(-128 to 128).

int nSomeInt= '2';

Here, 'nSomeInt' is not the value 2, it is 50.

int nSomeInt= 2;

Here, 'nSomeInt' is the value 2.

This is where you appear confused.

Viggy

[Paul McKenzie]

I don't know why bjarne stroustrup break convention to start counting from 0 rather than 1.

C++ has its roots in the 'C' language, and in 'C', array indices start from 0. The inventors of the C language are Brian Kernighan and Dennis Ritchie, not Bjarne Stroustrup.

Regards,

Paul McKenzie

[vkash]

C++ has its roots in the 'C' language, and in 'C', array indices start from 0. The inventors of the C language are Brian Kernighan and Dennis Ritchie, not Bjarne Stroustrup.

Regards,

Paul McKenzie

OK.

.

I am not confused. It is the way of my writing that giving you impression that i am confused. My bad knowledge of English is also responsible for this.