From 0a53f3622fde26367c5e5753ce4f2bb5320950e4 Mon Sep 17 00:00:00 2001
From: Fred Douglas <fredlas@willowbench.bio>
Date: Sun, 29 Jun 2025 16:15:46 -0500
Subject: [PATCH] throw exception when chr1 > chr2 passed to MatrixZoomData
 ctor

---
 C++/straw.cpp | 21 ++++++++-------------
 1 file changed, 8 insertions(+), 13 deletions(-)

diff --git a/C++/straw.cpp b/C++/straw.cpp
index 45a5ba9..a36cbc4 100644
--- a/C++/straw.cpp
+++ b/C++/straw.cpp
@@ -1322,19 +1322,14 @@ class MatrixZoomData {
                    const string &fileName) {
         this->version = version;
         this->fileName = fileName;
-        int32_t c01 = chrom1.index;
-        int32_t c02 = chrom2.index;
-        if (c01 <= c02) { // default is ok
-            this->c1 = c01;
-            this->c2 = c02;
-            this->numBins1 = static_cast<int32_t>(chrom1.length / resolution);
-            this->numBins2 = static_cast<int32_t>(chrom2.length / resolution);
-        } else { // flip
-            this->c1 = c02;
-            this->c2 = c01;
-            this->numBins1 = static_cast<int32_t>(chrom2.length / resolution);
-            this->numBins2 = static_cast<int32_t>(chrom1.length / resolution);
-        }
+        if (chrom1.index > chrom2.index) { // forbid non-canonical ordering
+            throw std::runtime_error("Lower-numbered chromosome must come first; MatrixZoomData was given: " +
+                                     std::to_string(chrom1.index) + ", " + std::to_string(chrom2.index));
+        }
+        this->c1 = chrom1.index;
+        this->c2 = chrom2.index;
+        this->numBins1 = static_cast<int32_t>(chrom1.length / resolution);
+        this->numBins2 = static_cast<int32_t>(chrom2.length / resolution);
         isIntra = c1 == c2;
 
         this->matrixType = matrixType;