def _coerce_map_from_(self, S):
"""
Return a coerce map from ``S``.
EXAMPLES::
sage: f = QQ.coerce_map_from(ZZ); f # indirect doctest
Natural morphism:
From: Integer Ring
To: Rational Field
sage: f(3)
3
sage: f(3^99) - 3^99
0
sage: f = QQ.coerce_map_from(int); f # indirect doctest
Native morphism:
From: Set of Python objects of type 'int'
To: Rational Field
sage: f(44)
44
::
sage: QQ.coerce_map_from(long) # indirect doctest
Composite map:
From: Set of Python objects of type 'long'
To: Rational Field
Defn: Native morphism:
From: Set of Python objects of type 'long'
To: Integer Ring
then
Natural morphism:
From: Integer Ring
To: Rational Field
"""
global ZZ
if ZZ is None:
import integer_ring
ZZ = integer_ring.ZZ
if S is ZZ:
return rational.Z_to_Q()
elif S is int:
return rational.int_to_Q()
elif ZZ.has_coerce_map_from(S):
return rational.Z_to_Q() * ZZ.coerce_map_from(S)
def _coerce_map_from_(self, S):
"""
Return a coerce map from ``S``.
EXAMPLES::
sage: f = QQ.coerce_map_from(ZZ); f # indirect doctest
Natural morphism:
From: Integer Ring
To: Rational Field
sage: f(3)
3
sage: f(3^99) - 3^99
0
sage: f = QQ.coerce_map_from(int); f # indirect doctest
Native morphism:
From: Set of Python objects of type 'int'
To: Rational Field
sage: f(44)
44
::
sage: QQ.coerce_map_from(long) # indirect doctest
Composite map:
From: Set of Python objects of type 'long'
To: Rational Field
Defn: Native morphism:
From: Set of Python objects of type 'long'
To: Integer Ring
then
Natural morphism:
From: Integer Ring
To: Rational Field
"""
global ZZ
if ZZ is None:
import integer_ring
ZZ = integer_ring.ZZ
if S is ZZ:
return rational.Z_to_Q()
elif S is int:
return rational.int_to_Q()
elif ZZ.has_coerce_map_from(S):
return rational.Z_to_Q() * ZZ.coerce_map_from(S)
