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Add a warning not to use coerce actions outside of the coercion model
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@simon-king-jena
simon-king-jena committed Apr 17, 2015
1 parent ced7bfc commit ef3bb5d
Showing 1 changed file with 87 additions and 16 deletions.
103 changes: 87 additions & 16 deletions src/sage/structure/coerce_actions.pyx
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Original file line number Diff line number Diff line change
Expand Up @@ -63,7 +63,12 @@ cdef class GenericAction(Action):

def __init__(self, Parent G, S, is_left, bint check=True):
"""
TESTS::
TESTS:
Note that coerce actions should only be used inside of the coercion
model. For this test, we need to strongly reference the domains,
for otherwise they could be garbage collected, giving rise to
random errors. ::
sage: M = MatrixSpace(ZZ,2)
sage: sage.structure.coerce_actions.ActedUponAction(M, Cusps, True)
Expand Down Expand Up @@ -94,7 +99,13 @@ cdef class GenericAction(Action):
result elements live. Typically, this should be the same as the
acted upon set.
EXAMPLES::
EXAMPLES:
Note that coerce actions should only be used inside of the coercion
model. For this test, we need to strongly reference the domains, for
otherwise they could be garbage collected, giving rise to random
errors. ::
sage: M = MatrixSpace(ZZ,2)
sage: A = sage.structure.coerce_actions.ActedUponAction(M, Cusps, True)
Expand All @@ -106,6 +117,7 @@ cdef class GenericAction(Action):
sage: A = sage.structure.coerce_actions.ActOnAction(S3, QQxyz, False)
sage: A.codomain()
Multivariate Polynomial Ring in x, y, z over Rational Field
"""
if self._codomain is None:
self._codomain = parent_c(self.act(an_element(self.G),
Expand Down Expand Up @@ -164,7 +176,12 @@ def detect_element_action(Parent X, Y, bint X_on_left, X_el=None, Y_el=None):
r"""
Returns an action of X on Y or Y on X as defined by elements X, if any.
EXAMPLES::
EXAMPLES:
Note that coerce actions should only be used inside of the coercion
model. For this test, we need to strongly reference the domains,
for otherwise they could be garbage collected, giving rise to
random errors. ::
sage: from sage.structure.coerce_actions import detect_element_action
sage: ZZx = ZZ['x']
Expand Down Expand Up @@ -272,7 +289,12 @@ cdef class ModuleAction(Action):
base ring. The simplest example to keep in mind is R acting on the
polynomial ring R[x].
EXAMPLES::
EXAMPLES:
Note that coerce actions should only be used inside of the coercion
model. For this test, we need to strongly reference the domains,
for otherwise they could be garbage collected, giving rise to
random errors. ::
sage: from sage.structure.coerce_actions import LeftModuleAction
sage: ZZx = ZZ['x']
Expand Down Expand Up @@ -361,7 +383,12 @@ cdef class ModuleAction(Action):
"""
The default name of this action type, which is has a sane default.
EXAMPLES::
EXAMPLES:
Note that coerce actions should only be used inside of the
coercion model. For this test, we need to strongly reference the
domains, for otherwise they could be garbage collected, giving rise to
random errors. ::
sage: from sage.structure.coerce_actions import LeftModuleAction, RightModuleAction
sage: ZZx = ZZ['x']
Expand All @@ -374,17 +401,24 @@ cdef class ModuleAction(Action):
sage: GF5t = GF5[['t']]
sage: RightModuleAction(GF5, GF5t)
Right scalar multiplication by Finite Field of size 5 on Power Series Ring in t over Finite Field of size 5
"""
return "scalar multiplication"

def codomain(self):
"""
The codomain of self, which may or may not be equal to the domain.
EXAMPLES::
EXAMPLES:
Note that coerce actions should only be used inside of the coercion
model. For this test, we need to strongly reference the domains,
for otherwise they could be garbage collected, giving rise to
random errors. ::
sage: from sage.structure.coerce_actions import LeftModuleAction
sage: A = LeftModuleAction(QQ, ZZ['x,y,z'])
sage: ZZxyz = ZZ['x,y,z']
sage: A = LeftModuleAction(QQ, ZZxyz)
sage: A.codomain()
Multivariate Polynomial Ring in x, y, z over Rational Field
"""
Expand All @@ -396,18 +430,29 @@ cdef class ModuleAction(Action):
"""
The domain of self, which is the module that is being acted on.
EXAMPLES::
EXAMPLES:
Note that coerce actions should only be used inside of the coercion
model. For this test, we need to strongly reference the domains,
for otherwise they could be garbage collected, giving rise to
random errors. ::
sage: from sage.structure.coerce_actions import LeftModuleAction
sage: A = LeftModuleAction(QQ, ZZ['x,y,z'])
sage: ZZxyz = ZZ['x,y,z']
sage: A = LeftModuleAction(QQ, ZZxyz)
sage: A.domain()
Multivariate Polynomial Ring in x, y, z over Integer Ring
"""
return self.underlying_set()

def __invert__(self):
"""
EXAMPLES::
EXAMPLES:
Note that coerce actions should only be used inside of the coercion
model. For this test, we need to strongly reference the domains, for
otherwise they could be garbage collected, giving rise to random
errors. ::
sage: from sage.structure.coerce_actions import RightModuleAction
Expand Down Expand Up @@ -499,7 +544,12 @@ cdef class LeftModuleAction(ModuleAction):
first argument (the left side) and the module element as the second
argument (the right side).
EXAMPLES::
EXAMPLES:
Note that coerce actions should only be used inside of the coercion
model. For this test, we need to strongly reference the domains,
for otherwise they could be garbage collected, giving rise to
random errors. ::
sage: from sage.structure.coerce_actions import LeftModuleAction
sage: R.<x> = QQ['x']
Expand Down Expand Up @@ -531,7 +581,12 @@ cdef class RightModuleAction(ModuleAction):
first argument (the left side) and the ring element as the second
argument (the right side).
EXAMPLES::
EXAMPLES:
Note that coerce actions should only be used inside of the coercion
model. For this test, we need to strongly reference the domains,
for otherwise they could be garbage collected, giving rise to
random errors. ::
sage: from sage.structure.coerce_actions import RightModuleAction
sage: R.<x> = QQ['x']
Expand Down Expand Up @@ -573,6 +628,12 @@ cdef class IntegerMulAction(Action):
Both addition and negation must be defined on the set `M`.
NOTE:
This class is used internally in Sage's coercion model. Outside of the
coercion model, special precautions are needed to prevent domains of
the action from being garbage collected.
INPUT:
- An integer ring, ``ZZ``
Expand Down Expand Up @@ -601,7 +662,12 @@ cdef class IntegerMulAction(Action):

cpdef _call_(self, nn, a):
"""
EXAMPLES::
EXAMPLES:
Note that coerce actions should only be used inside of the coercion
model. For this test, we need to strongly reference the field
``GF(101)``, for otherwise it could be garbage collected, giving rise
to random errors. ::
sage: from sage.structure.coerce_actions import IntegerMulAction
sage: GF101 = GF(101)
Expand All @@ -624,8 +690,7 @@ cdef class IntegerMulAction(Action):
This used to hang before :trac:`17844`::
sage: GF5 = GF(5)
sage: E = EllipticCurve(GF5, [4,0])
sage: E = EllipticCurve(GF(5), [4,0])
sage: P = E.random_element()
sage: (-2^63)*P
(0 : 1 : 0)
Expand All @@ -636,6 +701,7 @@ cdef class IntegerMulAction(Action):
Traceback (most recent call last):
...
AlarmInterrupt
"""
if not self._is_left:
a, nn = nn, a
Expand All @@ -660,7 +726,12 @@ cdef class IntegerMulAction(Action):

def _repr_name_(self):
"""
EXAMPLES::
EXAMPLES:
Note that coerce actions should only be used inside of the coercion
model. For this test, we need to strongly reference the field
``GF(5)``, for otherwise it could be garbage collected, giving rise
to random errors. ::
sage: from sage.structure.coerce_actions import IntegerMulAction
sage: GF5 = GF(5)
Expand Down

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