Add SparseTable constructor for initializer list, and a test.

Author: Atgeirr Flø Rasmussen

opm/grid/utility/SparseTable.hpp

@@ -44,6 +44,7 @@
 
 #include <algorithm>
 #include <cassert>
+#include <initializer_list>
 #include <numeric>
 #include <ostream>
 #include <type_traits>
@@ -148,6 +149,16 @@ struct PoisonIterator {
         }
 
 
+        /// Initializer list constructor for easy construction of small SparseTables.
+        SparseTable(std::initializer_list<std::initializer_list<T>> initlist) requires (std::is_same_v<Storage<T>, std::vector<T>>)
+        {
+            row_start_.push_back(0);
+            for (const auto& row : initlist) {
+                data_.insert(data_.end(), row);
+                row_start_.push_back(data_.size());
+            }
+        }
+
         /// Sets the table to contain the given data, organized into
         /// rows as indicated by the given row sizes.
         /// \param data_beg The start of the table data.

tests/test_sparsetable.cpp

@@ -108,6 +108,10 @@ BOOST_AUTO_TEST_CASE(construction_and_queries)
     }
     BOOST_CHECK(st2 == st2_allocate);
 
+    // Test initializer_list constructor.
+    const SparseTable<int> st2_initlist = { {0}, {}, {1, 2}, {3, 4, 5, 6}, {7, 8, 9} };
+    BOOST_CHECK(st2 == st2_initlist);
+
     // One element too few.
     BOOST_CHECK_THROW(const SparseTable<int> st3(elem, elem + num_elem - 1, rowsizes, rowsizes + num_rows), std::exception);