CODEWITHSUNDEEP
c++11syntax
levzettelin
levzettelin

Reputation: 2962

Second scope after struct definition

I looked a bit into Eric Nieblers range library https://github.com/ericniebler/range-v3/ and there (/include/range/v3/utility/concepts.hpp, line 36) I found code of the form

constexpr struct valid_expr_t
{
    template<typename ...T>
    true_ operator()(T &&...) const;
} valid_expr {};

I am confused to the second scope/braces after valid_expr. What is the meaning of the whole construct. Is this even a struct definition? The syntax seems not allowed in C++98. What can go into these second pair of braces?

Upvotes: 1

Views: 43

Answers (1)

Some programmer dude
Some programmer dude

Reputation: 409176

It's the C++11 uniform initialization syntax, and it simply initializes the valid_expr object.

It's like doing

struct valid_expr_t
{
    template<typename ...T>
    true_ operator()(T &&...) const;
};

constexpr valid_expr_t valid_expr {};

Upvotes: 4

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