Improve doctest coverage for sage.rings.qqbar

[loefflerd]

... from its current abysmal 45% (112 of 244) to something a bit more respectable.

Part of the meta-ticket #12024. See also #12665 (a bug discovered in working on this ticket).

CC: @sagetrac-JStarx

Component: doctest coverage

Author: David Loeffler

Reviewer: Jim Stark

Merged: sage-5.0.beta11

Issue created by migration from https://trac.sagemath.org/ticket/12662

[loefflerd]

Attachment: trac_12662-qqbar-doctest.patch.gz

Patch against 5.0.beta7

[loefflerd]

Description changed:

--- 
+++ 
@@ -1 +1,3 @@
 ... from its current abysmal 45% (112 of 244) to something a bit more respectable.
+
+Part of the meta-ticket #12024. See also #12665 (a bug discovered in working on this ticket).

[loefflerd]

Author: David Loeffler

[loefflerd]

comment:1

Here's a patch which gets full doctest coverage.

[orlitzky]

comment:2

Can't we just get rid of this stuff? If anyone misses it, it's in the mercurial history.

-    def gens(self):
-        return(QQbar_I, )
-
-    def gen(self, n=0):
-        if n == 0:
-            return QQbar_I
-        else:
-            raise IndexError, "n must be 0"
-
-    def ngens(self):
-        return 1
+# more nonsense -- DL
+#
+#    def gens(self):
+#        return(QQbar_I, )
+#
+#    def gen(self, n=0):
+#        if n == 0:
+#            return QQbar_I
+#        else:
+#            raise IndexError("n must be 0")
+#
+#    def ngens(self):
+#        return 1

[sagetrac-JStarx]

comment:3

The functions gen, gens, and ngens override methods from ParentWithGens and _is_valid_homomorphism_ overrides a method from Parent. If you don't override them then calling them will return a NotImplementedError which doesn't seem wise as they are used, for example _is_valid_homomorphism_ is called by the init method of RingHomomorphism_im_gens.

Also I do think they make mathematical sense. A field is generated by a single element, the 1 of the field, and for a homomorphism of fields we must send 1 to 1.

[loefflerd]

Work Issues: uncomment generators methods

[loefflerd]

comment:5

All right, I'll put them back in.