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Faster cardinality and repr implementation of Set_object_enumerated #41182

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Faster cardinality and repr implementation of Set_object_enumerated #41182

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28 changes: 27 additions & 1 deletion src/sage/sets/set.py
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Original file line number Diff line number Diff line change
Expand Up @@ -899,9 +899,19 @@ def cardinality(self):

sage: Set([1,1]).cardinality()
1
sage: Set(GF(998244353)).cardinality()
998244353
"""
from sage.rings.integer import Integer
return Integer(len(self.set()))
o = self.object()
if o is self:
Comment on lines +906 to +907
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@mantepse mantepse Nov 17, 2025

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how can o is self happen?

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@user202729 user202729 Nov 17, 2025 •
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Set_object_binary does Set_object.__init__(self, self, category=category)

many of them override this method, but better safe than sorry.

(seriously it's probably better to not make Set_object_binary inherit from Set_object at all... but I consider that out of scope)

return Integer(len(self.set()))
if isinstance(o, (list, tuple, set, frozenset)):
return Integer(len(o))
try:
return o.cardinality()
except (AttributeError, NotImplementedError):
return Integer(len(self.set()))

def __len__(self):
"""
Expand Down Expand Up @@ -957,7 +967,23 @@ def _repr_(self):

sage: Set()
{}
sage: repr(Set(GF(998244353))).replace("...", "LITERAL ELLIPSIS")
'Set of elements of Finite Field of size 998244353 = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9,
10, 11, 12, 13, 14, 15, 16, 17, 18, 19, LITERAL ELLIPSIS}'
"""
try:
if self.cardinality() > 20:
from itertools import islice
o = self.object()
l = list(islice(o, 0, 20))
s = "{" + ", ".join(map(repr, l)) + ", ...}"
assert len(l) == 20, (f"incorrect cardinality {self.cardinality()} "
f"reported for object type {type(self)} containing {l}")
if o is not self: # safeguard infinite loop if subclass is weird
s = f"Set of elements of {o!r} = {s}"
return s
except NotImplementedError:
pass
py_set = self.set()
if not py_set:
return "{}"
Expand Down
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