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c++templatesconstants
Kian
Kian

Reputation: 1684

How can I declare a template constant type?

If I make a typedef such as 

typedef int const cint;

cint will refer to an int that can't be modified. I can use cint in any context that takes a type (template parameter, function definition, etc).

However, typedefs don't work with templates. My hope is to be able to declare a template like Constant<SomeType> and have this refer to a const SomeType, the way I can do with cint above. Is it possible?

Upvotes: 4

Views: 684

Answers (2)

aschepler
aschepler

Reputation: 72356

std::add_const_t<SomeType> is the same as const SomeType.

Upvotes: 5

Piotr Skotnicki
Piotr Skotnicki

Reputation: 48467

C++11:

template <typename T>
using Constant = const T;

Constant<int> i = 1;
//! i = 2; // error: assignment of read-only variable 'i'

C++03:

template <typename T>
struct Constant
{
    typedef const T type;
};

Constant<int>::type i = 1;

Upvotes: 8

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