From ffbd5f7aee3280e92cdb6a9eb7c709e6c243c0a9 Mon Sep 17 00:00:00 2001
From: Davide Faconti <davide.faconti@gmail.com>
Date: Sun, 1 Feb 2026 18:38:42 +0100
Subject: [PATCH] Fix #974: numeric comparison for string-valued blackboard
 entries in scripts

---
 .../behaviortree_cpp/scripting/operators.hpp  | 30 +++++++++++++++---
 tests/gtest_blackboard.cpp                    | 31 +++++++++++++++++++
 2 files changed, 57 insertions(+), 4 deletions(-)

diff --git a/include/behaviortree_cpp/scripting/operators.hpp b/include/behaviortree_cpp/scripting/operators.hpp
index bd6bfc863..cb61ce631 100644
--- a/include/behaviortree_cpp/scripting/operators.hpp
+++ b/include/behaviortree_cpp/scripting/operators.hpp
@@ -16,6 +16,7 @@
 #include "behaviortree_cpp/scripting/script_parser.hpp"
 
 #include <cmath>
+#include <cstdlib>
 #include <memory>
 #include <string>
 #include <vector>
@@ -407,11 +408,32 @@ struct ExprComparison : ExprBase
       }
       else if(lhs_v.isString() && rhs_v.isString())
       {
-        auto lv = lhs_v.cast<SimpleString>();
-        auto rv = rhs_v.cast<SimpleString>();
-        if(!SwitchImpl(lv, rv, ops[i]))
+        // Try numeric comparison when both strings are parseable as numbers.
+        // This handles values set via blackboard->set(key, "42"). Issue #974.
+        auto ls = lhs_v.cast<std::string>();
+        auto rs = rhs_v.cast<std::string>();
+        char* lend = nullptr;
+        char* rend = nullptr;
+        double ld = std::strtod(ls.c_str(), &lend);
+        double rd = std::strtod(rs.c_str(), &rend);
+        bool l_numeric = (lend == ls.c_str() + ls.size()) && !ls.empty();
+        bool r_numeric = (rend == rs.c_str() + rs.size()) && !rs.empty();
+
+        if(l_numeric && r_numeric)
         {
-          return False;
+          if(!SwitchImpl(ld, rd, ops[i]))
+          {
+            return False;
+          }
+        }
+        else
+        {
+          auto lv = lhs_v.cast<SimpleString>();
+          auto rv = rhs_v.cast<SimpleString>();
+          if(!SwitchImpl(lv, rv, ops[i]))
+          {
+            return False;
+          }
         }
       }
       else if(lhs_v.isString() && rhs_v.isNumber())
diff --git a/tests/gtest_blackboard.cpp b/tests/gtest_blackboard.cpp
index 2c10e78d8..41f6008c9 100644
--- a/tests/gtest_blackboard.cpp
+++ b/tests/gtest_blackboard.cpp
@@ -745,3 +745,34 @@ TEST(BlackboardTest, SetBlackboard_WithPortRemapping)
   // Tick till the end with no crashes
   ASSERT_NO_THROW(tree.tickWhileRunning(););
 }
+
+// Issue #974: blackboard->set(key, "42") stores a string.
+// When two string-valued blackboard entries are compared in a script,
+// numeric comparison should be used if both strings are parseable as numbers.
+// "9" < "10" is false lexicographically but true numerically.
+TEST(BlackboardTest, StringSetNumericScriptComparison_Issue974)
+{
+  auto bb = Blackboard::create();
+  bb->set("a", std::string("9"));
+  bb->set("b", std::string("10"));
+
+  BehaviorTreeFactory factory;
+
+  std::string xml_txt = R"(
+    <root BTCPP_format="4" >
+      <BehaviorTree ID="Main">
+        <Sequence>
+          <Script code=" result := false "/>
+          <Script code=" result := (a < b) "/>
+          <AlwaysSuccess _successIf="result"/>
+        </Sequence>
+      </BehaviorTree>
+    </root>)";
+
+  auto tree = factory.createTreeFromText(xml_txt, bb);
+  auto status = tree.tickWhileRunning();
+
+  ASSERT_EQ(status, NodeStatus::SUCCESS);
+  // 9 < 10 is true numerically, even though "9" > "10" lexicographically
+  ASSERT_TRUE(bb->get<bool>("result"));
+}