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Merge pull request #34 from morinmorin/fix_result_of_usage

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Fix result_of usage
This commit is contained in:
Andrey Semashev 2017-09-11 23:44:36 +03:00 committed by GitHub
commit 07afd26ca2
1 changed files with 23 additions and 4 deletions
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27
include/boost/iterator/function_input_iterator.hpp
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@ -20,19 +20,38 @@
#include <boost/optional/optional.hpp>
#include <boost/utility/result_of.hpp>
#ifdef BOOST_RESULT_OF_USE_TR1
#include <boost/type_traits/is_function.hpp>
#endif
namespace boost {
namespace iterators {
namespace impl {
// Computes the return type of an lvalue-call with an empty argument,
// i.e. decltype(declval<F&>()()). F should be a nullary lvalue-callable
// or function.
template <class F>
struct result_of_nullary_lvalue_call
{
typedef typename result_of<
#ifdef BOOST_RESULT_OF_USE_TR1
typename mpl::if_<is_function<F>, F&, F>::type()
#else
F&()
#endif
>::type type;
};
template <class Function, class Input>
class function_input_iterator
: public iterator_facade<
function_input_iterator<Function, Input>,
typename result_of<Function ()>::type,
typename result_of_nullary_lvalue_call<Function>::type,
single_pass_traversal_tag,
typename result_of<Function ()>::type const &
typename result_of_nullary_lvalue_call<Function>::type const &
>
{
public:
@ -48,7 +67,7 @@ namespace iterators {
++state;
}
typename result_of<Function ()>::type const &
typename result_of_nullary_lvalue_call<Function>::type const &
dereference() const {
return (value ? value : value = (*f)()).get();
}
@ -60,7 +79,7 @@ namespace iterators {
private:
Function * f;
Input state;
mutable optional<typename result_of<Function ()>::type> value;
mutable optional<typename result_of_nullary_lvalue_call<Function>::type> value;
};
template <class Function, class Input>