From f6519405708ae283e566d8bb71e72603bbb9f260 Mon Sep 17 00:00:00 2001
From: q66 <daniel@octaforge.org>
Date: Sun, 27 Mar 2016 21:06:00 +0100
Subject: [PATCH] add initial implementation of range joiner (join any
 type-compatible ranges into one)

---
 examples/range.cc   |  25 +++++++--
 ostd/range.hh       | 125 ++++++++++++++++++++++++++++++++++++++++++++
 ostd/type_traits.hh |   4 +-
 3 files changed, 148 insertions(+), 6 deletions(-)

diff --git a/examples/range.cc b/examples/range.cc
index f61e284..2b8c296 100644
--- a/examples/range.cc
+++ b/examples/range.cc
@@ -5,23 +5,40 @@
 using namespace ostd;
 
 int main() {
-    /* range iter */
+    /* range iter - prints 0 to 9 each on new line */
     writeln("range iter test");
     for (int i: range(10))
         writeln(i);
 
-    /* algorithm: map */
+    /* algorithm: map - prints 0.5 to 9.5 each on new line */
     writeln("range map test");
     for (float f: map(range(10), [](int v) { return v + 0.5f; }))
         writeln(f);
 
-    /* alrogithm: filter */
+    /* algorithm: filter - prints 10, 15, 8 each on new line */
     writeln("range filter test");
     auto il = { 5, 5, 5, 5, 5, 10, 15, 4, 8, 2 };
     for (int i: filter(iter(il), [](int v) { return v > 5; }))
         writeln(i);
 
-    /* generate string ABCDEF */
+    /* prints ABCDEF (ASCII 65, 66, 67, 68, 69, 70) */
     String s(map(range(6), [](int v) -> char { return v + 65; }));
     writeln(s);
+
+    /* join a few ranges together - prints 11, 22, 33 ... 99 each on new line */
+    auto x = { 11, 22, 33 };
+    auto y = { 44, 55, 66 };
+    auto z = { 77, 88, 99 };
+    for (auto i: join(iter(x), iter(y), iter(z))) {
+        writeln(i);
+    }
+
+    /* chunk a range into subranges - prints
+     * {11, 22, 33}
+     * {44, 55, 66}
+     * {77, 88, 99}
+     */
+    auto cr = { 11, 22, 33, 44, 55, 66, 77, 88, 99 };
+    for (auto r: chunks(iter(cr), 3))
+        writeln(r);
 }
diff --git a/ostd/range.hh b/ostd/range.hh
index 7a5c555..8eeeb54 100644
--- a/ostd/range.hh
+++ b/ostd/range.hh
@@ -13,6 +13,7 @@
 #include "ostd/types.hh"
 #include "ostd/utility.hh"
 #include "ostd/type_traits.hh"
+#include "ostd/tuple.hh"
 
 namespace ostd {
 
@@ -1215,6 +1216,130 @@ ChunksRange<T> chunks(const T &it, RangeSize<T> chs) {
     return ChunksRange<T>(it, chs);
 }
 
+namespace detail {
+    template<Size I, Size N>
+    struct TupleEmptyRanges {
+        template<typename T>
+        static bool empty(const T &tup) {
+            if (!ostd::get<I>(tup).empty())
+                return false;
+            return TupleEmptyRanges<I + 1, N>::empty(tup);
+        }
+    };
+
+    template<Size N>
+    struct TupleEmptyRanges<N, N> {
+        template<typename T>
+        static bool empty(const T &) {
+            return true;
+        }
+    };
+
+    template<Size I, Size N>
+    struct TupleEqualRanges {
+        template<typename T>
+        static bool equal(const T &tup1, const T &tup2) {
+            if (!ostd::get<I>(tup1).equals_front(ostd::get<I>(tup2)))
+                return false;
+            return TupleEqualRanges<I + 1, N>::empty(tup1, tup2);
+        }
+    };
+
+    template<Size N>
+    struct TupleEqualRanges<N, N> {
+        template<typename T>
+        static bool equal(const T &, const T &) {
+            return true;
+        }
+    };
+
+    template<Size I, Size N>
+    struct TuplePopRanges {
+        template<typename T>
+        static bool pop(T &tup) {
+            if (!ostd::get<I>(tup).empty()) {
+                return ostd::get<I>(tup).pop_front();
+            }
+            return TuplePopRanges<I + 1, N>::pop(tup);
+        }
+    };
+
+    template<Size N>
+    struct TuplePopRanges<N, N> {
+        template<typename T>
+        static bool pop(T &) {
+            return false;
+        }
+    };
+
+    template<Size I, Size N, typename T>
+    struct TupleRangeFront {
+        template<typename U>
+        static T front(const U &tup) {
+            if (!ostd::get<I>(tup).empty()) {
+                return ostd::get<I>(tup).front();
+            }
+            return TupleRangeFront<I + 1, N, T>::front(tup);
+        }
+    };
+
+    template<Size N, typename T>
+    struct TupleRangeFront<N, N, T> {
+        template<typename U>
+        static T front(const U &tup) {
+            return ostd::get<0>(tup).front();
+        }
+    };
+}
+
+template<typename ...R>
+struct JoinRange: InputRange<JoinRange<R...>,
+    CommonType<ForwardRangeTag, RangeCategory<R>...>,
+    CommonType<RangeValue<R>...>, CommonType<RangeReference<R>...>,
+    CommonType<RangeSize<R>...>, CommonType<RangeDifference<R>...>> {
+private:
+    Tuple<R...> p_ranges;
+public:
+    JoinRange() = delete;
+    JoinRange(const R &...ranges): p_ranges(ranges...) {}
+    JoinRange(R &&...ranges): p_ranges(forward<R>(ranges)...) {}
+    JoinRange(const JoinRange &v): p_ranges(v.p_ranges) {}
+    JoinRange(JoinRange &&v): p_ranges(move(v.p_ranges)) {}
+
+    JoinRange &operator=(const JoinRange &v) {
+        p_ranges = v.p_ranges;
+        return *this;
+    }
+
+    JoinRange &operator=(JoinRange &&v) {
+        p_ranges = move(v.p_ranges);
+        return *this;
+    }
+
+    bool empty() const {
+        return detail::TupleEmptyRanges<0, sizeof...(R)>::empty(p_ranges);
+    }
+
+    bool equals_front(const JoinRange &r) const {
+        return detail::TupleEqualRanges<0, sizeof...(R)>::equal(p_ranges,
+            r.p_ranges);
+    }
+
+    bool pop_front() {
+        return detail::TuplePopRanges<0, sizeof...(R)>::pop(p_ranges);
+    }
+
+    CommonType<RangeReference<R>...> front() const {
+        return detail::TupleRangeFront<0, sizeof...(R),
+            CommonType<RangeReference<R>...>>::front(p_ranges);
+    }
+};
+
+template<typename R1, typename R2, typename ...R>
+JoinRange<R1, R2, R...> join(R1 r1, R2 r2, R ...rr) {
+    return JoinRange<R1, R2, R...>(move(r1), move(r2), move(rr)...);
+}
+
 template<typename T>
 struct AppenderRange: OutputRange<AppenderRange<T>, typename T::Value,
     typename T::Reference, typename T::Size, typename T::Difference> {
diff --git a/ostd/type_traits.hh b/ostd/type_traits.hh
index 4fcd4e7..49aaecb 100644
--- a/ostd/type_traits.hh
+++ b/ostd/type_traits.hh
@@ -1095,8 +1095,8 @@ namespace detail {
     };
 }
 
-template<typename T, typename U, typename ...V>
-using CommonType = typename detail::CommonTypeBase<T, U, V...>::Type;
+template<typename ...A>
+using CommonType = typename detail::CommonTypeBase<A...>::Type;
 
 /* aligned storage */