From 8d3ccd935d1a3b367822298745b324e7c687ae99 Mon Sep 17 00:00:00 2001
From: "Zed A. Shaw" <zed.shaw@gmail.com>
Date: Fri, 10 Jan 2025 10:59:23 -0500
Subject: [PATCH] Bringing in Amit's matrix for study and comparison.

---
 scratchpad/amitmatrix.hpp | 105 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 105 insertions(+)
 create mode 100644 scratchpad/amitmatrix.hpp

diff --git a/scratchpad/amitmatrix.hpp b/scratchpad/amitmatrix.hpp
new file mode 100644
index 0000000..c7e47f9
--- /dev/null
+++ b/scratchpad/amitmatrix.hpp
@@ -0,0 +1,105 @@
+#pragma once
+
+#include <cassert>
+#include <type_traits>
+#include <vector>
+#include <ostream>
+
+namespace amt {
+
+  template <typename T>
+    requires std::is_integral_v<T>
+    struct Matrix {
+      using base_type = std::vector<T>;
+      using value_type = typename base_type::value_type;
+      using pointer = typename base_type::pointer;
+      using const_pointer = typename base_type::const_pointer;
+      using reference = typename base_type::reference;
+      using const_reference = typename base_type::const_reference;
+      using iterator = typename base_type::iterator;
+      using const_iterator = typename base_type::const_iterator;
+      using size_type = std::size_t;
+
+      template <bool IsConst>
+        struct View {
+          using base_type = std::conditional_t<IsConst, const_pointer, pointer>;
+          base_type data;
+          size_type size;
+
+          constexpr auto operator[](size_type k) const noexcept {
+            assert(k < size && "Out of bound access");
+            return data[k];
+          }
+
+          constexpr auto operator[](size_type k) noexcept requires (!IsConst) {
+            assert(k < size && "Out of bound access");
+            return data[k];
+          }
+        };
+
+      constexpr Matrix() noexcept = default;
+      constexpr Matrix(Matrix const&) = default;
+      constexpr Matrix& operator=(Matrix const&) = default;
+      constexpr Matrix(Matrix &&) noexcept = default;
+      constexpr Matrix& operator=(Matrix &&) noexcept = default;
+      constexpr ~Matrix() = default;
+
+
+      Matrix(size_type row, size_type col, value_type def = {})
+        : m_data(row * col, def)
+        , m_row(row)
+        , m_col(col)
+        {}
+
+      constexpr bool empty() const noexcept { return m_data.empty(); };
+      constexpr bool size() const noexcept { return m_data.size(); };
+      constexpr size_type rows() const noexcept { return m_row; };
+      constexpr size_type cols() const noexcept { return m_col; };
+
+      constexpr iterator begin() noexcept { return m_data.begin(); }
+      constexpr iterator end() noexcept { return m_data.end(); }
+      constexpr const_iterator begin() const noexcept { return m_data.begin(); }
+      constexpr const_iterator end() const noexcept { return m_data.end(); }
+
+      constexpr auto operator()(size_type r, size_type c) noexcept -> reference {
+        auto const index = r * m_col + c; // column-major;
+        assert(index < size() && "Out of bound access");
+        return m_data[index];
+      }
+
+      constexpr auto operator()(size_type r, size_type c) const noexcept -> const_reference {
+        auto const index = r * m_col + c; // column-major;
+        assert(index < size() && "Out of bound access");
+        return m_data[index];
+      }
+
+      constexpr auto operator[](size_type r) noexcept -> View<false> {
+        auto const base = r * m_col;
+        assert(r < rows() && "Out of bound access");
+        return { .data = m_data.data() + base, .size = m_col };
+      }
+
+      constexpr auto operator[](size_type r) const noexcept -> View<true> {
+        auto const base = r * m_col;
+        assert(r < rows() && "Out of bound access");
+        return { .data = m_data.data() + base, .size = m_col };
+      }
+
+      friend std::ostream& operator<<(std::ostream& os, Matrix const& m) {
+        os << "[\n";
+        for (auto i = size_type{}; i < m.rows(); ++i) {
+          for (auto j = size_type{}; j < m.cols(); ++j) {
+            os << m[i][j] << ", ";
+          }
+          os << '\n';
+        }
+        return os << "]";
+      }
+
+      private:
+      base_type m_data;
+      size_type m_row{};
+      size_type m_col{};
+    };
+
+} // namespace amt