From a584bf54d842b885ce5f0d37bfa5d837db167f8c Mon Sep 17 00:00:00 2001
From: NADAL Jean-Baptiste <jbnadal@cabassegroup.com>
Date: Fri, 2 Feb 2024 17:41:51 +0100
Subject: [PATCH] [FEAT] Add Submatrix

---
 raytracing/src/matrix.cpp | 18 ++++++++++++++++++
 raytracing/src/matrix.h   |  1 +
 tests/03_matrix.cpp       | 38 ++++++++++++++++++++++++++++++++++++++
 3 files changed, 57 insertions(+)

diff --git a/raytracing/src/matrix.cpp b/raytracing/src/matrix.cpp
index 04faed2..e1fbfa0 100644
--- a/raytracing/src/matrix.cpp
+++ b/raytracing/src/matrix.cpp
@@ -208,6 +208,24 @@ double Matrix::determinant(void)
 
 /* ------------------------------------------------------------------------- */
 
+Matrix Matrix::sub_matrix(uint8_t a_rows, uint8_t a_cols)
+{
+    Matrix the_sub = *this;
+
+    the_sub.m_data.erase(the_sub.m_data.begin() + a_rows);
+    the_sub.m_rows--;
+
+    for (int the_row = 0; the_row < the_sub.m_rows; the_row++)
+    {
+        the_sub.m_data[the_row].erase(the_sub.m_data[the_row].begin() + a_cols);
+    }
+    the_sub.m_cols--;
+
+    return the_sub;
+}
+
+/* ------------------------------------------------------------------------- */
+
 Matrix Matrix::identity(void)
 {
     Matrix the_identity = {
diff --git a/raytracing/src/matrix.h b/raytracing/src/matrix.h
index 71d6a82..1754eb3 100644
--- a/raytracing/src/matrix.h
+++ b/raytracing/src/matrix.h
@@ -61,6 +61,7 @@ namespace Raytracer
 
         bool transpose(void);
         double determinant(void);
+        Matrix sub_matrix(uint8_t a_rows, uint8_t a_cols);
 
         static Matrix identity(void);
 
diff --git a/tests/03_matrix.cpp b/tests/03_matrix.cpp
index 31c213e..c8f5a9f 100644
--- a/tests/03_matrix.cpp
+++ b/tests/03_matrix.cpp
@@ -239,3 +239,41 @@ TEST_CASE("[Matrix] Calculating the determinant of a 2x2 matrix", "[Matrix]")
 
     REQUIRE(a.determinant() == 17);
 }
+
+/* ------------------------------------------------------------------------- */
+
+TEST_CASE("[Matrix] A submatrix of a 3x3 matrix is a 2x2 matrix", "[Matrix]")
+{
+    Matrix a = {
+        { 1, 5,  0},
+        {-3, 2,  7},
+        { 0, 6, -3}
+    };
+
+    Matrix b = {
+        {-3, 2},
+        { 0, 6}
+    };
+
+    REQUIRE(a.sub_matrix(0, 2) == b);
+}
+
+/* ------------------------------------------------------------------------- */
+
+TEST_CASE("[Matrix] A submatrix of a 4x4 matrix is a 3x3 matrix", "[Matrix]")
+{
+    Matrix a = {
+        {-6, 1,  1, 6},
+        {-8, 5,  8, 6},
+        {-1, 0,  8, 2},
+        {-7, 1, -1, 1}
+    };
+
+    Matrix b = {
+        {-6,  1, 6},
+        {-8,  8, 6},
+        {-7, -1, 1}
+    };
+
+    REQUIRE(a.sub_matrix(2, 1) == b);
+}