How to assign value to part of array?

[justforfun]

For example,

char *flag = new char [5];
flag[0] = 0xA;
flag[1] = 0x2;
flag[2] = 0x4;
flag[3] = 0x8;
flag[4] = 0x9;

But it is not a good way. Some other way like below could be better. But Qt doesn't support it. Does anyone know how to do similarly? Thanks!

flag[0..4] = 0x9842A;

Or just assign value to part of the array, like below. How to do similarly? Thanks!

flag[1..3] = 0x842;

[kalle]

@char flag[] = { 0xA, 0x2, 0x4, 0x8, 0x9 };@

That is really something that is or is not provided by the language (C++ in this case), not by the application framework.

[andre]

Well, you could always do this:
[code]for (int i(1); i<4; i++)
flag[i] = 0x9842A;
[/code]

Sure, the sugar is not as nice as what you post, but AFAIK, C++ does not support that, not even in the new upcomming c++0x. Your version is more efficient at runtime though, if your compiler is not smart enough to unroll the loop...

edit: thanks for the correction, I was a bit distracted. I do know how to write a for loop :-)

[DenisKormalev]

Andre, looks like you forgot mask for hex value (to assign only one byte at a time).

[lyuts]

C++0x will allow array initialization lists. I hope it comes out soon.

[justforfun]

Thank all of you for your comments!

I tested below program and the result is followed. By this way, it should work as I want.

@ char flag = new char [5];
for (int i=1; i<4; i++)
{
flag[i] = 0x090804020A>>(i8);
printf("%d, flag=%x\n", i, flag[i]);
}

int j=0;
printf("%d, flag=%x\n", j, flag[j]);
int k=4;
printf("%d, flag=%x\n", k, flag[k]);@

Result:

1, flag=2
2, flag=4
3, flag=8
0, flag=38
4, flag=78

[lyuts]

I got what you tried to do, but this way is not efficient in my opinion. Wouldn't that be easier to do with a union?

@union T
{
unsigned long long i;
char c[5];
};

T t;
t.i = 0x090804020A;
// ...
// further work with t.c@

[goetz]

That's heavily platform dependend: size of unsigned long long, 32 or 64 bit architecture, compiler, endianess.

Why not use "QByteArray":http://doc.qt.nokia.com/4.7/qbytearray.html?

[justforfun]

Hi, please notice that my focus is how to assign value to part of the array and in the same time not influence the rest part of the array.

[goetz]

Then these are your friends:

@
QByteArray & QByteArray::replace ( int pos, int len, const QByteArray & after );
QByteArray & QByteArray::replace ( int pos, int len, const char * after, int alen )
@