From: Michael Orlitzky <michael@orlitzky.com>
Date: Fri, 26 Jul 2019 16:45:19 +0000 (-0400)
Subject: eja: add __invert__ method for morphisms.
X-Git-Url: http://gitweb.michael.orlitzky.com/?a=commitdiff_plain;h=9866a99126ab5ec1e71b7a9c43ba5924ebfc6baf;p=sage.d.git

eja: add __invert__ method for morphisms.
---

diff --git a/mjo/eja/euclidean_jordan_algebra.py b/mjo/eja/euclidean_jordan_algebra.py
index fa11aed..78fa6b7 100644
--- a/mjo/eja/euclidean_jordan_algebra.py
+++ b/mjo/eja/euclidean_jordan_algebra.py
@@ -16,8 +16,10 @@ from sage.algebras.finite_dimensional_algebras.finite_dimensional_algebra_morphi
 
 class FiniteDimensionalEuclideanJordanAlgebraMorphism(FiniteDimensionalAlgebraMorphism):
     """
-    A very thin wrapper around FiniteDimensionalAlgebraMorphism that
-    does only three things:
+    A linear map between two finite-dimensional EJAs.
+
+    This is a very thin wrapper around FiniteDimensionalAlgebraMorphism
+    that does only a few things:
 
       1. Avoids the ``unitary`` and ``check`` arguments to the constructor
          that will always be ``False``. This is necessary because these
@@ -85,6 +87,44 @@ class FiniteDimensionalEuclideanJordanAlgebraMorphism(FiniteDimensionalAlgebraMo
                                                   check=False)
 
 
+    def __invert__(self):
+        """
+        EXAMPLES::
+
+            sage: J = RealSymmetricEJA(2)
+            sage: x = J.linear_combination(zip(range(len(J.gens())), J.gens()))
+            sage: x.is_invertible()
+            True
+            sage: ~x.operator()
+            Morphism from Euclidean Jordan algebra of degree 3 over Rational
+            Field to Euclidean Jordan algebra of degree 3 over Rational Field
+            given by matrix
+            [-3/2    2 -1/2]
+            [   1    0    0]
+            [-1/2    0  1/2]
+            sage: x.operator_matrix().inverse()
+            [-3/2    2 -1/2]
+            [   1    0    0]
+            [-1/2    0  1/2]
+
+        TESTS::
+
+            sage: set_random_seed()
+            sage: J = random_eja()
+            sage: x = J.random_element()
+            sage: not x.is_invertible() or (
+            ....:   (~x.operator()).matrix() == x.operator_matrix().inverse() )
+            True
+
+        """
+        A = self.matrix()
+        if not A.is_invertible():
+            raise ValueError("morphism is not invertible")
+
+        P = self.parent()
+        return FiniteDimensionalEuclideanJordanAlgebraMorphism(self.parent(),
+                                                                A.inverse())
+
     def _repr_(self):
         """
         We override only the representation that is shown to the user,