From 98440cba734ae198a813f078a2f81efafefa8725 Mon Sep 17 00:00:00 2001
From: Metin Cakircali <metin.cakircali@ecmwf.int>
Date: Tue, 21 Nov 2023 14:19:46 +0100
Subject: [PATCH] add support for by < 0

---
 src/metkit/mars/TypeToByListFloat.cc | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/src/metkit/mars/TypeToByListFloat.cc b/src/metkit/mars/TypeToByListFloat.cc
index 3450cb0..ee7a9de 100644
--- a/src/metkit/mars/TypeToByListFloat.cc
+++ b/src/metkit/mars/TypeToByListFloat.cc
@@ -61,11 +61,14 @@ void TypeToByListFloat::expand(const MarsExpandContext& ctx, std::vector<std::st
                 i += 2;
             }
 
-            ASSERT_MSG(from <= to, name_ + ": [" + std::to_string(from) + "] value must be less than [" +
-                                       std::to_string(to) + "] value!");
-            ASSERT_MSG(by > 0, name_ + ": [" + std::to_string(by) + "] value must be a positive number!");
-            for (float j = from + by; j <= to; j += by) {
-                newval.push_back(l2s(j));
+            if (by > 0) {
+                ASSERT_MSG(from <= to, name_ + ": [" + std::to_string(from) + "] value must be less than [" +
+                                           std::to_string(to) + "] value!");
+                for (float j = from + by; j <= to; j += by) { newval.push_back(l2s(j)); }
+            } else if (by < 0) {
+                ASSERT_MSG(from >= to, name_ + ": [" + std::to_string(from) + "] value must be greater than [" +
+                                           std::to_string(to) + "] value!");
+                for (float j = from + by; j >= to; j += by) { newval.push_back(l2s(j)); }
             }
 
             i++;