From 379f7cf646c9543868ae1262fd3cf9e79f537c9a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Daniel=20Ekl=C3=B6f?= <daniel@ekloef.se>
Date: Wed, 10 Jul 2019 19:17:53 +0200
Subject: [PATCH] grid: swap_row: drop requirement that row indices be positive

---
 grid.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/grid.c b/grid.c
index 2ffae9a3..a3f77dba 100644
--- a/grid.c
+++ b/grid.c
@@ -12,12 +12,13 @@ grid_swap_row(struct grid *grid, int row_a, int row_b)
 {
     assert(grid->offset >= 0);
     assert(row_a != row_b);
-    assert(row_a >= 0);
-    assert(row_b >= 0);
 
     int real_a = (grid->offset + row_a + grid->num_rows) % grid->num_rows;
     int real_b = (grid->offset + row_b + grid->num_rows) % grid->num_rows;
 
+    assert(real_a >= 0);
+    assert(real_b >= 0);
+
     struct row *tmp = grid->rows[real_a];
     grid->rows[real_a] = grid->rows[real_b];
     grid->rows[real_b] = tmp;