From: Michael Orlitzky <michael@orlitzky.com>
Date: Wed, 12 Nov 2025 00:51:51 +0000 (-0500)
Subject: mjo/cone/decomposition.py: add new is_reducible() function
X-Git-Url: http://gitweb.michael.orlitzky.com/?a=commitdiff_plain;h=7f0c67f42d8f2f0fdc78e2a431f712744136b4e5;p=sage.d.git

mjo/cone/decomposition.py: add new is_reducible() function
---

diff --git a/mjo/cone/decomposition.py b/mjo/cone/decomposition.py
index 31a4e3f..a21b0ec 100644
--- a/mjo/cone/decomposition.py
+++ b/mjo/cone/decomposition.py
@@ -199,3 +199,30 @@ def irreducible_factors(K):
         # equivalent but unequal copy of the input cone.
         return {K}
     return { Cone(K.rays(c)) for c in G.connected_components() }
+
+
+def is_reducible(K):
+    r"""
+    Return whether or not this cone is reducible.
+
+    A pointed convex cone ``K`` is reducible if some other cone
+    appears in its :func:`irreducible_factors`.
+
+    SETUP::
+
+        sage: from mjo.cone.decomposition import is_reducible
+
+    EXAMPLES:
+
+    The nonnegative orthant is always reducible in dimension two or
+    more::
+
+        sage: is_reducible(cones.nonnegative_orthant(1))
+        False
+        sage: is_reducible(cones.nonnegative_orthant(2))
+        True
+        sage: is_reducible(cones.nonnegative_orthant(3))
+        True
+
+    """
+    return len(irreducible_factors(K)) > 1