From d47f6f996d8104514447cc56bf60730053a87253 Mon Sep 17 00:00:00 2001
From: "Zed A. Shaw" <zed.shaw@gmail.com>
Date: Thu, 16 Jan 2025 13:38:14 -0500
Subject: [PATCH] Bring in a row major version of Amit's matrix.

---
 amt/matrix.hpp | 36 +++++++++++++++++++-----------------
 1 file changed, 19 insertions(+), 17 deletions(-)

diff --git a/amt/matrix.hpp b/amt/matrix.hpp
index 73c2eaf..6bd67ab 100644
--- a/amt/matrix.hpp
+++ b/amt/matrix.hpp
@@ -1,4 +1,5 @@
-#pragma once
+#ifndef AMT_MATRIX_HPP
+#define AMT_MATRIX_HPP
 
 #include <cassert>
 #include <cstddef>
@@ -82,7 +83,7 @@ namespace amt {
 		}
 
 		Matrix(std::initializer_list<std::initializer_list<value_type>> li)
-			: m_row(li.size())
+			: m_row(li.size())	
 		{
 			for (auto const& row: li) {
 				m_col = std::max(m_col, row.size());
@@ -119,28 +120,28 @@ namespace amt {
 		constexpr const_reverse_iterator rbegin() const noexcept { return std::reverse_iterator(end()); }
 		constexpr const_reverse_iterator rend() const noexcept { return std::reverse_iterator(begin()); }
 
-		constexpr auto operator()(size_type r, size_type c) noexcept -> reference {
-			auto const index = r * m_col + c; // column-major;
+			constexpr auto operator()(size_type r, size_type c) noexcept -> reference {
+			auto const index = r + c * m_row; // row-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;
+			auto const index = r + c * m_row; // row-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 + base, .size = m_col };
+		constexpr auto operator[](size_type c) noexcept -> View<false> {
+			auto const base = c * m_row;
+			assert(c < cols() && "Out of bound access");
+			return { .data = m_data + base, .size = m_row };
 		}
 
-		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 + base, .size = m_col };
+		constexpr auto operator[](size_type c) const noexcept -> View<true> {
+			auto const base = c * m_row;
+			assert(c < cols() && "Out of bound access");
+			return { .data = m_data + base, .size = m_row };
 		}
 
 		friend void swap(Matrix& lhs, Matrix& rhs) noexcept {
@@ -158,7 +159,7 @@ namespace amt {
 
 } // namespace amt
 
-#if 0
+
 #include <format>
 namespace std {
 	template <typename T>
@@ -166,7 +167,7 @@ namespace std {
 		constexpr auto parse(format_parse_context& ctx) {
 			return ctx.begin();
 		}
-
+		
 		auto format(amt::Matrix<T> const& m, auto& ctx) const {
 			std::string s = "[\n";
 			for (auto r = std::size_t{}; r < m.rows(); ++r) {
@@ -174,11 +175,12 @@ namespace std {
 					s += std::format("{}, ", m(r, c));
 				}
 				s += '\n';
-			}
+			}	
 			s += "]";
 			return format_to(ctx.out(), "{}", s);
 		}
 	};
 
 } // namespace std
-#endif
+
+#endif // AMT_MATRIX_HPP