CODEWITHSUNDEEP
c++arraystemplates
jotaen
jotaen

Reputation: 7049

Array of non-type template?

I have a non-type template class Foo:

template <int n>
class Foo {
public:
  Foo(){}
};

How can I store multiple instances of that class in one array? (When the instances all have different template values.)

This, however, does not work:

Foo<int> myArray[] = {Foo<1>() , Foo<2>() , Foo<3>()};

Compiler error is: template argument for non-type template parameter must be an expression

Upvotes: 1

Views: 287

Answers (3)

spin_eight
spin_eight

Reputation: 4025

template <int n>
class Foo : public Ifoo {
public:
  Foo(){}
};

IFoo* myArray[] = {..

Upvotes: 1

Sean
Sean

Reputation: 62532

As had been mentioned, Foo<1> is a different type to Foo<2> etc etc, so you can't store them in an array.

To get around this you can de-template the class and make the integer a constructor argument instead:

class Foo {
public:
  Foo(int n){}
};

Foo myArray[] = {Foo(1) , Foo(2) , Foo(3)};

Upvotes: 1

Jarod42
Jarod42

Reputation: 218268

Foo<1> is not the same type as Foo<2> (and so on), so you can't store them in a array (if they derived from FooBase, you may have an array of FooBase*).

You may store them in a std::tuple:

auto foos = std::make_tuple(Foo<1>() , Foo<2>() , Foo<3>());

Upvotes: 6

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