Stating constant arrays value in C++

Question

For example I have:

int boo[8];
boo[1] = boo[3] = boo[7] = 4;
boo[0] = boo[2] = 7;
boo[4] = boo[5] = boo[6] = 15;

How I should type it as constant values? I saw similar question but it didn't help me.

EDIT: One more question what about if boo with indexes 0 1 3 4 5 6 7 is constant but boo[2] is not? is it possible to do it?

If by "constant values" you mean an initialization list, you can't. But some compilers provide interesting extensions. Take a look this question stackoverflow.com/questions/201101/… — Alexei Sholik
– Alexei Sholik, Commented Apr 7, 2011 at 13:47

Al Riddoch · Accepted Answer · 2011-04-07 14:05:07Z

7

Is this what you are looking for?

const int boo[] = { 7, 4, 7, 4, 15, 15, 15, 4 };

Get a non-const pointer to one entry in the array like this:

int * foo = (int*)&boo[2];

edited Apr 7, 2011 at 14:05

answered Apr 7, 2011 at 13:47

Al Riddoch

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3 Comments

Templar Over a year ago

Yes, one more question what about if boo with index 0 1 3 4 5 6 7 is constants but boo[2] is not?

BenjaminB Over a year ago

Maybe you can access it via a different pointer: int const* boo2 = boo+2; And after *boo2 = 5;

Al Riddoch Over a year ago

I have modified the answer to include an example of getting a pointer you can use to modify one entry.

BenjaminB · Accepted Answer · 2011-04-07 14:02:53Z

3

One not so elegant solution may be:

const int boo[8] = {7,4,7,4,15,15,15,4};

Another solution may be:

int boo_[8];
boo_[1] = boo_[3] = boo_[7] = 4;
boo_[0] = boo_[2] = 7;
boo_[4] = boo_[5] = boo_[6] = 15;
const int * boo = boo_;

edited Apr 7, 2011 at 14:02

answered Apr 7, 2011 at 13:51

BenjaminB

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2 Comments

x10 Over a year ago

Nah, it seems quite elegant to me :)

edA-qa mort-ora-y Over a year ago

Use boo_ instead of _boo. Names starting with underscores, or double underscores, are reserved for use by the implementation(compiler). There are certain rules here but its probably just best to avoid the underscore at the beginning all together.

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