From a6f4ecafb9aeb94bab65d0256d8d69ab0ed024b0 Mon Sep 17 00:00:00 2001
From: Jasper
Date: Fri, 12 Sep 2025 11:40:15 +0200
Subject: Matrix transpose doesn't edit memory representation

- transpose swaps dimensions
- transpose sets variable to indicate it has been transposed
- matrix_at acts accordingly
- matrix_foreach_idx now uses matrix_at to set the iterator to allow
  iterating over a transposed matrix
---
 matrix.c | 16 +++++++++++-----
 1 file changed, 11 insertions(+), 5 deletions(-)

(limited to 'matrix.c')

diff --git a/matrix.c b/matrix.c
index 646be42..222ad6d 100644
--- a/matrix.c
+++ b/matrix.c
@@ -20,6 +20,7 @@ Matrix *matrix_alloc(size_t m, size_t n)
     mat->xs = xs;
     mat->m = m;
     mat->n = n;
+    mat->T = false;
     return mat;
 }
 
@@ -196,14 +197,19 @@ double matrix_trace(const Matrix *mat)
 
 Matrix *matrix_transpose(const Matrix *mat)
 {
-    assert(mat != NULL && "Matrix points to null");
-    assert(mat->xs != NULL && "Matrix elements point to null");
-
-    Matrix *T = matrix_alloc(mat->n, mat->m);
-    matrix_foreach_idx(T, t, i, j) *t = matrix_at(mat, j, i);
+    Matrix *T = matrix_copy(mat);
+    matrix_transpose1(T);
     return T;
 }
 
+void matrix_transpose1(Matrix *mat)
+{
+    size_t m = mat->m;
+    mat->m = mat->n;
+    mat->n = m;
+    mat->T = !mat->T;
+}
+
 Matrix *matrix_add(const Matrix *A, const Matrix *B)
 {
     assert(A->m == B->m && A->n == B->n && "Dimension mismatch");
-- 
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