From: Michael Orlitzky <michael@orlitzky.com>
Date: Fri, 30 Aug 2019 00:32:55 +0000 (-0400)
Subject: eja: add "check" parameter to check if our field is real.
X-Git-Url: http://gitweb.michael.orlitzky.com/?p=sage.d.git;a=commitdiff_plain;h=49f266e16de87af712beb680570ff39e2ae87de4

eja: add "check" parameter to check if our field is real.
---

diff --git a/mjo/eja/TODO b/mjo/eja/TODO
index 51c2a33..b2495b5 100644
--- a/mjo/eja/TODO
+++ b/mjo/eja/TODO
@@ -17,5 +17,3 @@
 7. Do we really need to orthonormalize the basis in a subalgebra?
    So long as we can decompose the operator (which is invariant
    under changes of basis), who cares?
-
-8. Check that our field is a subring of RLF.
diff --git a/mjo/eja/eja_algebra.py b/mjo/eja/eja_algebra.py
index 430f233..7a65fab 100644
--- a/mjo/eja/eja_algebra.py
+++ b/mjo/eja/eja_algebra.py
@@ -16,12 +16,9 @@ from sage.misc.cachefunc import cached_method
 from sage.misc.prandom import choice
 from sage.misc.table import table
 from sage.modules.free_module import FreeModule, VectorSpace
-from sage.rings.integer_ring import ZZ
-from sage.rings.number_field.number_field import QuadraticField
-from sage.rings.polynomial.polynomial_ring_constructor import PolynomialRing
-from sage.rings.rational_field import QQ
-from sage.rings.real_lazy import CLF, RLF
-
+from sage.rings.all import (ZZ, QQ, RR, RLF, CLF,
+                            PolynomialRing,
+                            QuadraticField)
 from mjo.eja.eja_element import FiniteDimensionalEuclideanJordanAlgebraElement
 from mjo.eja.eja_utils import _mat2vec
 
@@ -40,11 +37,12 @@ class FiniteDimensionalEuclideanJordanAlgebra(CombinatorialFreeModule):
                  rank,
                  prefix='e',
                  category=None,
-                 natural_basis=None):
+                 natural_basis=None,
+                 check=True):
         """
         SETUP::
 
-            sage: from mjo.eja.eja_algebra import random_eja
+            sage: from mjo.eja.eja_algebra import (JordanSpinEJA, random_eja)
 
         EXAMPLES:
 
@@ -56,7 +54,23 @@ class FiniteDimensionalEuclideanJordanAlgebra(CombinatorialFreeModule):
             sage: x*y == y*x
             True
 
+        TESTS:
+
+        The ``field`` we're given must be real::
+
+            sage: JordanSpinEJA(2,QQbar)
+            Traceback (most recent call last):
+            ...
+            ValueError: field is not real
+
         """
+        if check:
+            if not field.is_subring(RR):
+                # Note: this does return true for the real algebraic
+                # field, and any quadratic field where we've specified
+                # a real embedding.
+                raise ValueError('field is not real')
+
         self._rank = rank
         self._natural_basis = natural_basis