[hist] Add RBinIndex conversion overloads

.github/workflows/histv7.yml

@@ -16,7 +16,7 @@ jobs:
       - name: Checkout
         uses: actions/checkout@v4
       - name: Configure
-        run: cmake -B build -DCMAKE_BUILD_TYPE=RelWithDebInfo -DCMAKE_INSTALL_PREFIX=install -Dhistv7_benchmark=ON hist/histv7
+        run: cmake -B build -DCMAKE_BUILD_TYPE=RelWithDebInfo -DCMAKE_CXX_FLAGS="-Werror -Wall -Wextra -Wpedantic -Wsign-conversion" -DCMAKE_INSTALL_PREFIX=install -Dhistv7_benchmark=ON hist/histv7
       - name: Build
         run: cmake --build build
       - name: Install

hist/histv7/inc/ROOT/RBinIndex.hxx

@@ -28,6 +28,9 @@ class RBinIndex final {
    // We use std::uint64_t instead of std::size_t for the index because for sparse histograms, not all bins have to be
    // allocated in memory. However, we require that the index has at least that size.
    static_assert(sizeof(std::uint64_t) >= sizeof(std::size_t), "index type not large enough to address all bins");
+   // During construction, we expect that any standard integer fits in std::uint64_t.
+   static_assert(sizeof(std::uint64_t) >= sizeof(unsigned long long),
+                 "index type not large enough to store any standard integer");
 
    std::uint64_t fIndex = kInvalidIndex;
 
@@ -36,7 +39,33 @@ public:
    RBinIndex() = default;
 
    /// Construct a bin index for a normal bin.
-   RBinIndex(std::uint64_t index) : fIndex(index) { assert(IsNormal()); }
+   RBinIndex(unsigned int index) : RBinIndex(static_cast<unsigned long long>(index)) {}
+
+   /// Construct a bin index for a normal bin.
+   RBinIndex(unsigned long index) : RBinIndex(static_cast<unsigned long long>(index)) {}
+
+   /// Construct a bin index for a normal bin.
+   RBinIndex(unsigned long long index) : fIndex(index) { assert(IsNormal()); }
+
+   /// Construct a bin index for a normal bin.
+   ///
+   /// \param[in] index signed integer that must not be negative
+   RBinIndex(int index) : RBinIndex(static_cast<long long>(index)) {}
+
+   /// Construct a bin index for a normal bin.
+   ///
+   /// \param[in] index signed integer that must not be negative
+   RBinIndex(long index) : RBinIndex(static_cast<long long>(index)) {}
+
+   /// Construct a bin index for a normal bin.
+   ///
+   /// \param[in] index signed integer that must not be negative
+   RBinIndex(long long index)
+   {
+      assert(index >= 0);
+      fIndex = static_cast<std::uint64_t>(index);
+      assert(IsNormal());
+   }
 
    /// Return the index for a normal bin.
    std::uint64_t GetIndex() const

hist/histv7/test/hist_index.cxx

@@ -4,6 +4,10 @@
 #include <iterator>
 #include <vector>
 
+#ifndef TYPED_TEST_SUITE
+#define TYPED_TEST_SUITE TYPED_TEST_CASE
+#endif
+
 TEST(RBinIndex, Constructor)
 {
    const RBinIndex invalid;
@@ -152,6 +156,20 @@ TEST(RBinIndex, Relation)
    EXPECT_FALSE(underflow >= overflow);
 }
 
+template <typename T>
+class RBinIndexConversion : public testing::Test {};
+
+using IntegerTypes = testing::Types<signed char, unsigned char, short, unsigned short, int, unsigned int, long,
+                                    unsigned long, long long, unsigned long long>;
+TYPED_TEST_SUITE(RBinIndexConversion, IntegerTypes);
+
+TYPED_TEST(RBinIndexConversion, Constructor)
+{
+   const TypeParam input = 1;
+   const RBinIndex index(input);
+   EXPECT_EQ(index.GetIndex(), 1);
+}
+
 using ROOT::Experimental::Internal::CreateBinIndexRange;
 
 TEST(RBinIndexRange, ConstructorCreate)