Fix clip function behavior when a_min is greater than a_max

Co-authored-by: Copilot <copilot@github.com>

Author: Alex-PLACET

include/xtensor/core/xmath.hpp

@@ -606,13 +606,13 @@ namespace xt
             template <class A1, class A2, class A3>
             constexpr auto operator()(const A1& v, const A2& lo, const A3& hi) const
             {
-                return xtl::select(v < lo, lo, xtl::select(hi < v, hi, v));
+                return xtl::select(lo < hi, xtl::select(v < lo, lo, xtl::select(hi < v, hi, v)), hi);
             }
 
             template <class A1, class A2, class A3>
             constexpr auto simd_apply(const A1& v, const A2& lo, const A3& hi) const
             {
-                return xt_simd::select(v < lo, lo, xt_simd::select(hi < v, hi, v));
+                return xt_simd::select(lo < hi, xt_simd::select(v < lo, lo, xt_simd::select(hi < v, hi, v)), hi);
             }
         };
 

test/test_xmath.cpp

@@ -222,6 +222,15 @@ namespace xt
         EXPECT_EQ(res1, clip(opt_a, 2.0, 4.0));
     }
 
+    TEST(xmath, clip_amin_greater_than_amax)
+    {
+        // NumPy-compatible behavior: when a_min > a_max, all values
+        // are set to a_max (the hi bound).
+        const xarray<int> arr = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9};
+        const xarray<int> expected = {1, 1, 1, 1, 1, 1, 1, 1, 1, 1};
+        EXPECT_EQ(expected, clip(arr, 8, 1));
+    }
+
     TEST(xmath, sign)
     {
         shape_type shape = {3, 2};