[with patch, positive review] the coercion code (in __mul__) should call __rmul__ when left or right is not coercible to a Sage element

[was]

In this example the last print statement goes boom, but should work fine.

class Foo:
   def __rmul__(self, left):
      return 'hello'

H = Foo()
print int(3)*H
print 3*H

[jason]

Currently, (before this patch), if a class did

_r_action = __rmul__

things would work since the coercion model looks for an _r_action function as a last resort. This patch just makes this line unnecessary by having the coercion system also look for an rmul function (which is standard python; see  http://docs.python.org/ref/numeric-types.html)

Apparently this patch is controversial to at least one person, so it probably ought to be discussed.

[jason]

disclaimer: I don't know much at all about the coercion system; the above statements are from observations made in running examples.

[jason]

credit goes to gfurnish for noticing and helping track down the segfault that the original patch introduced!

Apply coercion-rmul2.patch instead of coercion-rmul.patch

[jason]

(and gfurnish also knew how to fix the error causing the segfault!)

[jason]

The patches above apply to 2.10.2.

[was]

Looks good to me. Thanks guys!

[mabshoff]

Merged coercion-rmul2.patch in Sage 2.10.3.rc0