Thread: Is {0,} okay?

Hmm... I see. So the comma would say set every element before the last comma to whatever specified and everything after it to zero?

As in:

Code:

int array[5] = {2,}

// Is the same as

int array[5] = {2,0,0,0,0}

// ?

I guess that makes sense, but I still say it's not that explicit.

It's exactly the same with or without the comma.

[edit]
The last one, I mean.
[/edit]

Because you only gave one value during initialization here:

Code:

int array[20] = {2,};

If you did this instead:

Code:

int array[20] = {2,35,86,14};

Then it would show:
2
35
86
14
0
0
.
.
.
0
0

Originally Posted by SlyMaelstrom

Hmm... I see. So the comma would say set every element before the last comma to whatever specified and everything after it to zero?

As in:

Code:

int array[5] = {2,}

// Is the same as

int array[5] = {2,0,0,0,0}

// ?

I guess that makes sense, but I still say it's not that explicit.

It's also the same as

Code:

int array[5] = {2}

The comma means nothing.

Code:

int a[5] = {2,};

is exactly equivalent to:

Code:

int a[5] = {2};

They both mean the exact same thing to the compiler. The final comma is just optional. I'm guessing because it's easier to write a script that spits out a bunch of values followed by a comma rather than have to try to figure out which is the last value so you can omit the comma.

The comma has no effect. Period. It does nothing. The standard states, as I've just stated, that any elements you don't initialize, provided you have actually initialized at least one, will be set to zero.

Code:

int array[5] = { 1 };

This sets array[ 0 ] to 1, and since I haven't initialized any of the others, they get set to 0.

Code:

int array[5];

None of these get initialized to anything. They have whatever was in memory. No initialization is done.

Code:

int array[5] = { 0, 1 };

The first element I manually set to zero, the next I set to 1, and the rest are initialized automatically to zero.

It doesn't matter if there's a trailing comma. It has no effect. The comma does nothing.


Quzah.

Hmm, ok.

I was thinking:

Code:

int array[5] = { 2 } // would initialize every element to 2. 
// Isn't there a simple way to do that similar to this?

That's what I've been trying to find out (and Sly refuses to believe is "explicit").

Thanks.

Originally Posted by SlyMaelstrom

Hmm, ok.

I was thinking:

Code:

int array[5] = { 2 } // would initialize every element to 2. 
// Isn't there a simple way to do that similar to this?

Sure, use memset.

The reason you were thinking it filled them to 2, is because we're always doing this:

Code:

char array[BUFSIZ] = {0};

Which gives us a nicely zeroed array.


Quzah.

Yes, that's exactly right.

I've actually never had a situation where I've had to initialize a whole array to anything but 0.

The tricky one is automagically initializing a sequentially numbered array. Gone be the days of:

Code:

{
  int array[100], i;

  for(i = 0;i < 100;++i)
    array[i] = i;
}

If you figure that one out let me know

Code:

perl -e "foreach(0..100){print\"$_, \"}"

That might help.