CODEWITHSUNDEEP
c++templatesc++14
Dev Null
Dev Null

Reputation: 4997

How to define template function overload to match empty std::tuple<>?

I'd like to distinguish between empty and non-empty tuples, and I came up with the following solution (example):

#include <tuple>
#include <iostream>

template <typename ... Args>
void function(const std::tuple<Args...>& t)
{
    std::cout << "empty tuple" << std::endl;
}

template <typename Head, typename ... Args>
void function(const std::tuple<Head, Args...>& t)
{
    std::cout << "tuple of size: " << sizeof...(Args) + 1 << std::endl;
}

int main()
{
    function(std::make_tuple());  // picks 1st function
    function(std::make_tuple(1)); // picks 2nd function
    function(std::make_tuple(1, 2, 3, '4')); // picks 2nd function
}

However, using variadic Args to match std::tuple<> is misleading for a reader, and I think that introducing Head in the 2nd overload is excessive. Is there a simple way to write an overload that matches std::tuple<> directly?

Upvotes: 2

Views: 138

Answers (1)

Nir Friedman
Nir Friedman

Reputation: 17704

Did you try:

void function(const std::tuple<>& t) { ... }

?

Then you don't need to write Head out separately in the second function. Live example: http://coliru.stacked-crooked.com/a/1806c3a8a3e6b2d1.

Upvotes: 3

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