Added std::span constructor to HalfVector and SparseVector

Author: ankane

CHANGELOG.md

@@ -1,6 +1,7 @@
 ## 0.2.2 (unreleased)
 
 - Added map constructor to `SparseVector`
+- Added `std::span` constructor to `HalfVector` and `SparseVector`
 
 ## 0.2.1 (2025-01-15)
 

include/pgvector/halfvec.hpp

@@ -9,6 +9,10 @@
 #include <ostream>
 #include <vector>
 
+#if __cplusplus >= 202002L
+#include <span>
+#endif
+
 namespace pgvector {
 /// A half vector.
 class HalfVector {
@@ -28,6 +32,13 @@ class HalfVector {
         value_ = std::vector<float>{value, value + n};
     }
 
+#if __cplusplus >= 202002L
+    /// Creates a half vector from a span.
+    HalfVector(std::span<const float> value) {
+        value_ = std::vector<float>(value.begin(), value.end());
+    }
+#endif
+
     /// Returns the number of dimensions.
     size_t dimensions() const {
         return value_.size();

include/pgvector/sparsevec.hpp

@@ -38,6 +38,20 @@ class SparseVector {
         }
     }
 
+#if __cplusplus >= 202002L
+    /// Creates a sparse vector from a span.
+    SparseVector(std::span<const float> value) {
+        dimensions_ = value.size();
+        for (size_t i = 0; i < value.size(); i++) {
+            float v = value[i];
+            if (v != 0) {
+                indices_.push_back(i);
+                values_.push_back(v);
+            }
+        }
+    }
+#endif
+
     /// Creates a sparse vector from a map of non-zero elements.
     SparseVector(const std::unordered_map<int, float>& map, int dimensions) {
         if (dimensions < 1) {

include/pgvector/vector.hpp

@@ -33,6 +33,7 @@ class Vector {
     }
 
 #if __cplusplus >= 202002L
+    /// Creates a vector from a span.
     Vector(std::span<const float> value) {
         value_ = std::vector<float>(value.begin(), value.end());
     }

test/main.cpp

@@ -32,13 +32,27 @@ void test_halfvec() {
     assert(vec.dimensions() == 3);
 }
 
+#if __cplusplus >= 202002L
+void test_halfvec_span() {
+    auto vec = HalfVector(std::span<const float>({1, 2, 3}));
+    assert(vec.dimensions() == 3);
+}
+#endif
+
 void test_sparsevec() {
     auto vec = SparseVector({1, 0, 2, 0, 3, 0});
     assert(vec.dimensions() == 6);
     assert(vec.indices() == (std::vector<int>{0, 2, 4}));
     assert(vec.values() == (std::vector<float>{1, 2, 3}));
 }
 
+#if __cplusplus >= 202002L
+void test_sparsevec_span() {
+    auto vec = SparseVector(std::span<const float>({1, 0, 2, 0, 3, 0}));
+    assert(vec.dimensions() == 6);
+}
+#endif
+
 void test_sparsevec_map() {
     std::unordered_map<int, float> map = {{2, 2}, {4, 3}, {3, 0}, {0, 1}};
     auto vec = SparseVector(map, 6);
@@ -54,6 +68,12 @@ int main() {
     test_vector_span();
 #endif
     test_halfvec();
+#if __cplusplus >= 202002L
+    test_halfvec_span();
+#endif
     test_sparsevec();
+#if __cplusplus >= 202002L
+    test_sparsevec_span();
+#endif
     return 0;
 }