I want to write a function that can be used with an argument that otherwise could directly occur in a range-based loop:
template <typename Iterable>
void sayIt(const Iterable& stuff) {
for (const auto& e : stuff) {
cout << e << endl;
}
}
This works fine with stl containers and other types, but not with a brace-enclosed initializer:
std::vector<std::string> baz(2, "sorry");
sayIt(baz); // okay
sayIt({"foo", "bar"}); // not okay
Is there a way to make the function work with both?
Braced-init-list has no type and cause template argument deduction failing.
Non-deduced contexts
In the following cases, the types, templates, and non-type values that are used to compose P do not participate in template argument deduction, but instead use the template arguments that were either deduced elsewhere or explicitly specified. If a template parameter is used only in non-deduced contexts and is not explicitly specified, template argument deduction fails.
- The parameter P, whose A is a braced-init-list, but P is not std::initializer_list, a reference to one (possibly cv-qualified), or a reference to an array:
You can specify the template argument as std::initializer_list
explicitly to bypass the deduction,
sayIt<std::initializer_list<std::string>>({"foo", "bar"});
Or add another overload taking std::initializer_list
.
template <typename T>
void sayIt(std::initializer_list<T> stuff) {
sayIt<decltype(stuff)>(stuff);
}
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