C++ const variable in function declaration

Question

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What is the difference between const int*, const int * const, and int const *?

I am trying to understand how const works in a function parameter. What is the difference between void function(int const *&i); and void function(const int *&i);? And I would appreciate if you gave an example of their implementation and of the usage of i.

Marlon · Accepted Answer · 2011-05-02T19:36:30.793

3

They are the same, just read it from right to left:

First example: i is a reference to a pointer of a constant integer.

Second example: i is a reference to a pointer of an integer constant.

The placement of const only changes things on either side of the pointer. For example:

const int* i

means: i is a pointer to a constant integer

whereas int* const i

means: i is a constant pointer to an integer.

edited May 02 '11 at 19:36

answered May 02 '11 at 19:30

Marlon

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can I assign a variable to i in this function, if yes, how? – ibrahim May 02 '11 at 19:39
@ibrahim: Of course you can. You can do it as usual. Like this `i = p;` where `p` is some value implicitly convertible to `const int*`. – Serge Dundich May 02 '11 at 20:22

score 0 · Answer 2 · answered May 02 '11 at 19:28

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Those declarations are equivalent. For more info, see this page.

answered May 02 '11 at 19:28

Brian Kelly

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score 0 · Answer 3 · answered May 02 '11 at 19:28

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Best place for const correctness is the - C++ FAQ Lite

answered May 02 '11 at 19:28

naumcho

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score 0 · Answer 4 · answered May 02 '11 at 19:28

0

They're both the same.

It means a reference to a pointer to a const int.

answered May 02 '11 at 19:28

Mark B

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C++ const variable in function declaration

4 Answers4