Const array with variables from another const array

Question

I have an constant array like this:

const int foo[NUM] = {
    9000,
    4400,
    620,
    480,
    1620
};

How can I create another const array that will do some math operations on the variables from foo? I tried this:

const int bar[NUM] = {
    foo[0] / (DEFINE1* DEFINE2),
    foo[1] / (DEFINE1* DEFINE2),
    foo[2] / (DEFINE1* DEFINE2),
    foo[3] / (DEFINE1* DEFINE2),
    foo[4] / (DEFINE1* DEFINE2)
};

However this doesnt work, it returns errors:

Error 2 (near initialization for 'bar[0]'), for all elements

Error 1 initializer element is not constant, for all elements

cnicutar · Accepted Answer · 2015-01-11 13:24:50Z

5

C consts are not real constants, as described in this C FAQ. As such, the compiler only enforces that you can't write to them. For all other uses, they are not constants (the way your defines are).

Side note: this is one of the areas where C and C++ differ. In C++ const has a markedly different meaning, closer to what you are trying.

answered Jan 11, 2015 at 13:24

cnicutar

184k26 gold badges378 silver badges398 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

user1806687 Over a year ago

But even if I dont use const, just use int I get same errors... How can I fix this?

cnicutar Over a year ago

Removing const is not the solution. My answer was pointing out the reason it is not working. You can just use defines everywhere.

user1806687 Over a year ago

I cant really, some functions depend on arrays.

Community · Accepted Answer · 2017-05-23 12:11:45Z

2

cnicutar gives the answer to your question.

A possible work-around still following the DRY-principles would be:

#define FOO_0 (9000)
#define F00_1 (4400)
...

const int foo[NUM] = {
  FOO_0,
  FOO_1,
  ...
};

const int bar[NUM] = {
  FOO_0 / (DEFINE1* DEFINE2),
  FOO_1 / (DEFINE1* DEFINE2),
  ...
};

edited May 23, 2017 at 12:11

CommunityBot

11 silver badge

answered Jan 11, 2015 at 13:29

alk

71.2k10 gold badges112 silver badges274 bronze badges

1 Comment

user1806687 Over a year ago

I could use this, but the problem is I have another array that uses variables from bar... Is there another way? Its not necessary to use const int.

Collectives™ on Stack Overflow

Const array with variables from another const array

2 Answers 2

3 Comments

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

3 Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related