From 7cf41171a8b4a431f2f4f578729ec059c35e5140 Mon Sep 17 00:00:00 2001
From: Palash Tyagi <23239946+Magnus167@users.noreply.github.com>
Date: Thu, 1 May 2025 23:12:19 +0100
Subject: [PATCH] Allow creation of 0-row matrices from empty column data and
 improve data flattening in from_cols method.

---
 src/matrix/mat.rs | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/src/matrix/mat.rs b/src/matrix/mat.rs
index 07a3d3d..1523bf7 100644
--- a/src/matrix/mat.rs
+++ b/src/matrix/mat.rs
@@ -13,13 +13,15 @@ impl<T: Clone> Matrix<T> {
     pub fn from_cols(cols_data: Vec<Vec<T>>) -> Self {
         let cols = cols_data.len();
         assert!(cols > 0, "need at least one column");
-        let rows = cols_data[0].len();
-                                                            // Allow 0-row matrices if columns are empty, but not 0-col matrices if rows > 0
+        // Handle empty cols_data
+        let rows = cols_data.get(0).map_or(0, |c| c.len()); 
+        // Allow 0-row matrices if columns are empty, but not 0-col matrices if rows > 0
         assert!(
             rows > 0 || cols == 0,
             "need at least one row if columns exist"
         );
-        for (i, col) in cols_data.iter().enumerate().skip(1) {
+
+        for (i, col) in cols_data.iter().enumerate() {
             assert!(
                 col.len() == rows,
                 "col {} has len {}, expected {}",
@@ -28,10 +30,8 @@ impl<T: Clone> Matrix<T> {
                 rows
             );
         }
-        let mut data = Vec::with_capacity(rows * cols);
-        for col in cols_data {
-            data.extend(col);
-        }
+        // Flatten column data directly
+        let data = cols_data.into_iter().flatten().collect();
         Matrix { rows, cols, data }
     }