Make iterator_result_converter satisfy std::ranges::range
std::ranges::range requires the iterator to be default-constructible and have postfix operator++. Add those to satisfy the concept.
This commit is contained in:
parent
9fd0cc96a5
commit
932c8370d5
|
@ -11,9 +11,28 @@
|
||||||
#include "partial_range.h"
|
#include "partial_range.h"
|
||||||
|
|
||||||
template <typename result_type, typename iterator_type>
|
template <typename result_type, typename iterator_type>
|
||||||
|
/* Declare the requirements on the class itself, rather than the one method which needs them, because:
|
||||||
|
* - the class is useless if that one method fails its requirements
|
||||||
|
* - gcc produces better error messages if the class is rejected, than if the
|
||||||
|
* class is accepted and `operator*()` is rejected.
|
||||||
|
*/
|
||||||
|
requires(
|
||||||
|
requires(iterator_type i) {
|
||||||
|
/* If the base type's result cannot be converted to this type's result,
|
||||||
|
* then `operator*()` will raise an error when it attempts an implicit
|
||||||
|
* conversion.
|
||||||
|
*/
|
||||||
|
{*i} -> std::convertible_to<result_type>;
|
||||||
|
/* If `result_type` and the base type's `operator*` are the same, then
|
||||||
|
* this adapter has no effect.
|
||||||
|
*/
|
||||||
|
requires(!std::is_same<result_type, decltype(*i)>::value);
|
||||||
|
}
|
||||||
|
)
|
||||||
class iterator_result_converter : public iterator_type
|
class iterator_result_converter : public iterator_type
|
||||||
{
|
{
|
||||||
public:
|
public:
|
||||||
|
constexpr iterator_result_converter() = default;
|
||||||
iterator_result_converter(iterator_type &&iter) :
|
iterator_result_converter(iterator_type &&iter) :
|
||||||
iterator_type(std::move(iter))
|
iterator_type(std::move(iter))
|
||||||
{
|
{
|
||||||
|
@ -22,6 +41,10 @@ public:
|
||||||
{
|
{
|
||||||
return *this;
|
return *this;
|
||||||
}
|
}
|
||||||
|
/* `using iterator_type::operator*()` is not viable here because this
|
||||||
|
* `operator*()` has a different return type than
|
||||||
|
* `iterator_type::operator*()`.
|
||||||
|
*/
|
||||||
result_type operator*() const
|
result_type operator*() const
|
||||||
{
|
{
|
||||||
return this->iterator_type::operator*();
|
return this->iterator_type::operator*();
|
||||||
|
@ -30,6 +53,12 @@ public:
|
||||||
{
|
{
|
||||||
return static_cast<iterator_result_converter &>(this->iterator_type::operator++());
|
return static_cast<iterator_result_converter &>(this->iterator_type::operator++());
|
||||||
}
|
}
|
||||||
|
iterator_result_converter operator++(int)
|
||||||
|
{
|
||||||
|
auto r = *this;
|
||||||
|
this->iterator_type::operator++();
|
||||||
|
return r;
|
||||||
|
}
|
||||||
};
|
};
|
||||||
|
|
||||||
template <typename result_type, typename range_type, typename iterator_type = iterator_result_converter<result_type, decltype(std::begin(std::declval<range_type &>()))>>
|
template <typename result_type, typename range_type, typename iterator_type = iterator_result_converter<result_type, decltype(std::begin(std::declval<range_type &>()))>>
|
||||||
|
|
Loading…
Reference in a new issue