How can I declare a template constant type?

Question

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?

as simple as template <typename T> using Constant = const T; — Piotr Skotnicki
– Piotr Skotnicki, Commented Dec 17, 2014 at 18:46
template <typename T> using Constant = const T; @PiotrS. beat me by 7 sec :( — Borgleader
– Borgleader, Commented Dec 17, 2014 at 18:46
the comments should be answers, also, i dont' quiet remember but is "using" template usage a Cx11 feature? — Nicko Po
– Nicko Po, Commented Dec 17, 2014 at 18:49

Piotr Skotnicki · Accepted Answer · 2014-12-17 18:53:18Z

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;

aschepler · Accepted Answer · 2014-12-17 18:54:19Z

5

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

answered Dec 17, 2014 at 18:54

aschepler

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1 Comment

Piotr Skotnicki Over a year ago

I was just about to add this to my answer +1

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