[incubator-datasketches-cpp] 08/09: another attempt at MSVC compatibility

[jm...@apache.org]

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jmalkin pushed a commit to branch patch_for_rc4
in repository https://gitbox.apache.org/repos/asf/incubator-datasketches-cpp.git

commit 680ddc103443a0c5ada12e1ae9fa68496a3a34a3
Author: AlexanderSaydakov <Al...@users.noreply.github.com>
AuthorDate: Mon Jun 1 10:29:31 2020 -0700

    another attempt at MSVC compatibility
---
 theta/include/conditional_back_inserter.hpp | 9 +++++++++
 theta/include/theta_a_not_b.hpp             | 7 +++++++
 theta/include/theta_a_not_b_impl.hpp        | 4 ++--
 3 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/theta/include/conditional_back_inserter.hpp b/theta/include/conditional_back_inserter.hpp
index e9b0590..9b33833 100644
--- a/theta/include/conditional_back_inserter.hpp
+++ b/theta/include/conditional_back_inserter.hpp
@@ -31,6 +31,15 @@ public:
   template<typename P>
   conditional_back_insert_iterator(Container& c, P&& p): std::back_insert_iterator<Container>(c), p(std::forward<P>(p)) {}
 
+  // MSVC seems to insist on having copy constructor and assignment
+  conditional_back_insert_iterator(const conditional_back_insert_iterator& other):
+    std::back_insert_iterator<Container>(other), p(other.p) {}
+  conditional_back_insert_iterator& operator=(const conditional_back_insert_iterator& other) {
+    std::back_insert_iterator<Container>::operator=(other);
+    p = other.p;
+    return *this;
+  }
+
   conditional_back_insert_iterator& operator=(typename Container::const_reference value) {
     if (p(value)) std::back_insert_iterator<Container>::operator=(value);
     return *this;
diff --git a/theta/include/theta_a_not_b.hpp b/theta/include/theta_a_not_b.hpp
index 5287887..db66ac7 100644
--- a/theta/include/theta_a_not_b.hpp
+++ b/theta/include/theta_a_not_b.hpp
@@ -54,6 +54,13 @@ private:
   typedef typename std::allocator_traits<A>::template rebind_alloc<uint64_t> AllocU64;
   uint16_t seed_hash_;
 
+  class less_than {
+  public:
+    explicit less_than(uint64_t value): value(value) {}
+    bool operator()(uint64_t value) const { return value < this->value; }
+  private:
+    uint64_t value;
+  };
 };
 
 // alias with default allocator for convenience
diff --git a/theta/include/theta_a_not_b_impl.hpp b/theta/include/theta_a_not_b_impl.hpp
index 2ffca28..4343ee3 100644
--- a/theta/include/theta_a_not_b_impl.hpp
+++ b/theta/include/theta_a_not_b_impl.hpp
@@ -48,10 +48,10 @@ compact_theta_sketch_alloc<A> theta_a_not_b_alloc<A>::compute(const theta_sketch
   bool is_empty = a.is_empty();
 
   if (b.get_num_retained() == 0) {
-    std::copy_if(a.begin(), a.end(), std::back_inserter(keys), [theta](uint64_t key) { return key < theta; });
+    std::copy_if(a.begin(), a.end(), std::back_inserter(keys), less_than(theta));
   } else {
     if (a.is_ordered() && b.is_ordered()) { // sort-based
-      std::set_difference(a.begin(), a.end(), b.begin(), b.end(), conditional_back_inserter(keys, [theta](uint64_t key) { return key < theta; }));
+      std::set_difference(a.begin(), a.end(), b.begin(), b.end(), conditional_back_inserter(keys, less_than(theta)));
     } else { // hash-based
       const uint8_t lg_size = lg_size_from_count(b.get_num_retained(), update_theta_sketch_alloc<A>::REBUILD_THRESHOLD);
       vector_u64<A> b_hash_table(1 << lg_size, 0);


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