eja: another TODO.

[sage.d.git] / mjo / eja / TODO

diff --git a/mjo/eja/TODO b/mjo/eja/TODO
index f6d7743782613d241c50e05eee665d59278bd4b4..3c63d3b97796031de5ecf914f3051d8e47b93967 100644 (file)
--- a/mjo/eja/TODO
+++ b/mjo/eja/TODO
@@ -1,21 +1,38 @@
 1. Add CartesianProductEJA.
 
-2. Check the axioms in the constructor when check != False?
+2. Add references and start citing them.
 
-3. Add references and start citing them.
+3. Implement the octonion simple EJA.
 
-4. Implement the octonion simple EJA.
+4. Override random_instance(), one(), et cetera in DirectSumEJA.
 
-5. Factor out the unit-norm basis (and operator symmetry) tests once
-   all of the algebras pass.
+5. Switch to QQ in *all* algebras for _charpoly_coefficients().
+   This only works when we know that the basis can be rationalized...
+   which is the case at least for the concrete EJAs we provide,
+   but not in general.
 
-6. Refactor the current ungodly fast charpoly hack (relies on the
-   theory to ensure that the charpolys are equal.)
+6. Pass already_echelonized (default: False) and echelon_basis
+   (default: None) into the subalgebra constructor. The value of
+   already_echelonized can be passed to V.span_of_basis() to save
+   some time, and usinf e.g. FreeModule_submodule_with_basis_field
+   we may somehow be able to pass the echelon basis straight in to
+   save time.
 
-7. If we factor out a "matrix algebra" class, then it would make sense
-   to replace the custom embedding/unembedding functions with static
-   _real_embedding() and _real_unembedding() methods.
+   This may require supporting "basis" as a list of basis vectors
+   (as opposed to superalgebra elements) in the subalgebra constructor.
 
-8. Implement random_instance() for the main EJA class.
+7. The inner product should be an *argument* to the main EJA
+   constructor.  Afterwards, the basis normalization step should be
+   optional (and enabled by default) for ALL algebras, since any
+   algebra can have a nonstandard inner-product and its basis can be
+   normalized with respect to that inner- product. For example, the
+   HadamardEJA could be equipped with an inner- product that is twice
+   the usual one. Then for the basis to be orthonormal, we would need
+   to divide e.g. (1,0,0) by <(1,0,0),(1,0,0)> = 2 to normalize it.
 
-9. Implement random_instance() for the subalgebra class.
+8. Use charpoly for inverse itself?
+
+9. Pre-cache charpoly for some small algebras?
+
+10. Compute the scalar in the general natural_inner_product() for
+    matrices, so no overrides are necessary.
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