remove the range half stuff for now

doc/ranges.md

@@ -132,7 +132,7 @@ From forward ranges onwards, independence of state is guaranteed though.
 
 This method checks whether the range has any elements left in it. If this
 returns true, it means `front()` is safe to use. Safe code should always
-check; the behavior is an item is retrieved on an empty range.
+check; the behavior is undefined if an item is retrieved on an empty range.
 
 ~~~{.cc}
     bool equals_front() const;

ostd/range.hh

@@ -250,227 +250,6 @@ namespace detail {
     };
 }
 
-// range half
-
-template<typename T>
-struct half_range;
-
-namespace detail {
-    template<typename R, bool = is_bidirectional_range<typename R::range>>
-    struct range_add;
-
-    template<typename R>
-    struct range_add<R, true> {
-        using diff_t = range_difference_t<typename R::range>;
-
-        static diff_t add_n(R &half, diff_t n) {
-            if (n < 0) {
-                return -half.prev_n(n);
-            }
-            return half.next_n(n);
-        }
-        static diff_t sub_n(R &half, diff_t n) {
-            if (n < 0) {
-                return -half.next_n(n);
-            }
-            return half.prev_n(n);
-        }
-    };
-
-    template<typename R>
-    struct range_add<R, false> {
-        using diff_t = range_difference_t<typename R::range>;
-
-        static diff_t add_n(R &half, diff_t n) {
-            if (n < 0) {
-                return 0;
-            }
-            return half.next_n(n);
-        }
-        static diff_t sub_n(R &half, diff_t n) {
-            if (n < 0) {
-                return 0;
-            }
-            return half.prev_n(n);
-        }
-    };
-}
-
-namespace detail {
-    template<typename>
-    struct range_iterator_tag {
-        /* better range types all become random access iterators */
-        using type = std::random_access_iterator_tag;
-    };
-
-    template<>
-    struct range_iterator_tag<input_range_tag> {
-        using type = std::input_iterator_tag;
-    };
-
-    template<>
-    struct range_iterator_tag<output_range_tag> {
-        using type = std::output_iterator_tag;
-    };
-
-    template<>
-    struct range_iterator_tag<forward_range_tag> {
-        using type = std::forward_iterator_tag;
-    };
-
-    template<>
-    struct range_iterator_tag<bidirectional_range_tag> {
-        using type = std::bidirectional_iterator_tag;
-    };
-}
-
-template<typename T>
-struct range_half {
-private:
-    T p_range;
-public:
-    using range = T;
-
-    using iterator_category = typename detail::range_iterator_tag<T>::type;
-    using value_type        = range_value_t<T>;
-    using difference_type   = range_difference_t<T>;
-    using pointer           = range_value_t<T> *;
-    using reference         = range_reference_t<T>;
-
-    range_half() = delete;
-    range_half(T const &range): p_range(range) {}
-
-    template<typename U, typename = std::enable_if_t<std::is_convertible_v<U, T>>>
-    range_half(range_half<U> const &half): p_range(half.p_range) {}
-
-    range_half(range_half const &half): p_range(half.p_range) {}
-    range_half(range_half &&half): p_range(std::move(half.p_range)) {}
-
-    range_half &operator=(range_half const &half) {
-        p_range = half.p_range;
-        return *this;
-    }
-
-    range_half &operator=(range_half &&half) {
-        p_range = std::move(half.p_range);
-        return *this;
-    }
-
-    void next() { p_range.pop_front(); }
-    void prev() { p_range.push_front(); }
-
-    void next_n(range_size_t<T> n) {
-        p_range.pop_front_n(n);
-    }
-    void prev_n(range_size_t<T> n) {
-        p_range.push_front_n(n);
-    }
-
-    range_difference_t<T> add_n(range_difference_t<T> n) {
-        return detail::range_add<range_half<T>>::add_n(*this, n);
-    }
-    range_difference_t<T> sub_n(range_difference_t<T> n) {
-        return detail::range_add<range_half<T>>::sub_n(*this, n);
-    }
-
-    range_reference_t<T> get() const {
-        return p_range.front();
-    }
-
-    range_difference_t<T> distance(range_half const &half) const {
-        return p_range.distance_front(half.p_range);
-    }
-
-    bool equals(range_half const &half) const {
-        return p_range.equals_front(half.p_range);
-    }
-
-    bool operator==(range_half const &half) const {
-        return equals(half);
-    }
-    bool operator!=(range_half const &half) const {
-        return !equals(half);
-    }
-    bool operator<(range_half const &half) const {
-        return distance(half) > 0;
-    }
-    bool operator>(range_half const &half) const {
-        return distance(half) < 0;
-    }
-    bool operator<=(range_half const &half) const {
-        return distance(half) >= 0;
-    }
-    bool operator>=(range_half const &half) const {
-        return distance(half) <= 0;
-    }
-
-    /* iterator like interface */
-
-    range_reference_t<T> operator*() const {
-        return p_range.front();
-    }
-
-    range_reference_t<T> operator[](range_size_t<T> idx) const {
-        return p_range[idx];
-    }
-
-    range_half &operator++() {
-        next();
-        return *this;
-    }
-    range_half operator++(int) {
-        range_half tmp(*this);
-        next();
-        return tmp;
-    }
-
-    range_half &operator--() {
-        prev();
-        return *this;
-    }
-    range_half operator--(int) {
-        range_half tmp(*this);
-        prev();
-        return tmp;
-    }
-
-    range_half operator+(range_difference_t<T> n) const {
-        range_half tmp(*this);
-        tmp.add_n(n);
-        return tmp;
-    }
-    range_half operator-(range_difference_t<T> n) const {
-        range_half tmp(*this);
-        tmp.sub_n(n);
-        return tmp;
-    }
-
-    range_half &operator+=(range_difference_t<T> n) {
-        add_n(n);
-        return *this;
-    }
-    range_half &operator-=(range_difference_t<T> n) {
-        sub_n(n);
-        return *this;
-    }
-
-    T iter() const { return p_range; }
-
-    half_range<range_half> iter(range_half const &other) const {
-        return half_range<range_half>(*this, other);
-    }
-
-    range_value_t<T> *data() { return p_range.data(); }
-    range_value_t<T> const *data() const { return p_range.data(); }
-};
-
-template<typename R>
-inline range_difference_t<R> operator-(
-    range_half<R> const &lhs, range_half<R> const &rhs
-) {
-    return rhs.distance(lhs);
-}
-
 namespace detail {
     template<typename R>
     void pop_front_n(R &range, range_size_t<R> n) {
@@ -581,10 +360,6 @@ struct input_range {
         return zip_range<B, R1, RR...>(iter(), std::move(r1), std::move(rr)...);
     }
 
-    range_half<B> half() const {
-        return range_half<B>(iter());
-    }
-
     /* iterator like interface operating on the front part of the range
      * this is sometimes convenient as it can be used within expressions */
 
@@ -851,98 +626,6 @@ namespace detail {
     constexpr bool iterable_test = decltype(test_iterable<T>(0))::value;
 }
 
-template<typename T>
-struct half_range: input_range<half_range<T>> {
-    using range_category  = range_category_t  <typename T::range>;
-    using value_type      = range_value_t     <typename T::range>;
-    using reference       = range_reference_t <typename T::range>;
-    using size_type       = range_size_t      <typename T::range>;
-    using difference_type = range_difference_t<typename T::range>;
-
-private:
-    T p_beg;
-    T p_end;
-
-public:
-    half_range() = delete;
-    half_range(half_range const &range):
-        p_beg(range.p_beg), p_end(range.p_end)
-    {}
-    half_range(half_range &&range):
-        p_beg(std::move(range.p_beg)), p_end(std::move(range.p_end))
-    {}
-    half_range(T const &beg, T const &end):
-        p_beg(beg),p_end(end)
-    {}
-    half_range(T &&beg, T &&end):
-        p_beg(std::move(beg)), p_end(std::move(end))
-    {}
-
-    half_range &operator=(half_range const &range) {
-        p_beg = range.p_beg;
-        p_end = range.p_end;
-        return *this;
-    }
-
-    half_range &operator=(half_range &&range) {
-        p_beg = std::move(range.p_beg);
-        p_end = std::move(range.p_end);
-        return *this;
-    }
-
-    bool empty() const { return p_beg == p_end; }
-
-    void pop_front() {
-        p_beg.next();
-    }
-    void push_front() {
-        p_beg.prev();
-    }
-    void pop_back() {
-        p_end.prev();
-    }
-    void push_back() {
-        p_end.next();
-    }
-
-    reference front() const { return *p_beg; }
-    reference back() const { return *(p_end - 1); }
-
-    bool equals_front(half_range const &range) const {
-        return p_beg == range.p_beg;
-    }
-    bool equals_back(half_range const &range) const {
-        return p_end == range.p_end;
-    }
-
-    difference_type distance_front(half_range const &range) const {
-        return range.p_beg - p_beg;
-    }
-    difference_type distance_back(half_range const &range) const {
-        return range.p_end - p_end;
-    }
-
-    size_type size() const { return p_end - p_beg; }
-
-    half_range slice(size_type start, size_type end) const {
-        return half_range{p_beg + start, p_beg + end};
-    }
-
-    reference operator[](size_type idx) const {
-        return p_beg[idx];
-    }
-
-    void put(value_type const &v) {
-        p_beg.range().put(v);
-    }
-    void put(value_type &&v) {
-        p_beg.range().put(std::move(v));
-    }
-
-    value_type *data() { return p_beg.data(); }
-    value_type const *data() const { return p_beg.data(); }
-};
-
 template<typename T>
 struct reverse_range: input_range<reverse_range<T>> {
     using range_category  = std::common_type_t<