def _gen_names(elts):
r"""
Used to find a name for a generator when rings are created using the
``__getitem__`` syntax, e.g. ``ZZ['x']``, ``ZZ[sqrt(2)]``.
EXAMPLES::
sage: from sage.categories.rings import _gen_names
sage: list(_gen_names([sqrt(5)]))
['sqrt5']
sage: list(_gen_names([sqrt(-17), 2^(1/3)]))
['a', 'b']
sage: list(_gen_names((1..27)))[-1]
'aa'
"""
import re
from sage.structure.parent_gens import _certify_names
from sage.combinat.words.words import Words
it = iter(Words("abcdefghijklmnopqrstuvwxyz", infinite=False))
it.next() # skip empty word
for x in elts:
name = str(x)
m = re.match('^sqrt\((\d+)\)$', name)
if m:
name = "sqrt%s" % m.groups()[0]
try:
_certify_names([name])
except ValueError:
name = it.next().string_rep()
yield name
def _gen_names(elts):
r"""
Used to find a name for a generator when rings are created using the
``__getitem__`` syntax, e.g. ``ZZ['x']``, ``ZZ[sqrt(2)]``.
EXAMPLES::
sage: from sage.categories.rings import _gen_names
sage: list(_gen_names([sqrt(5)]))
['sqrt5']
sage: list(_gen_names([sqrt(-17), 2^(1/3)]))
['a', 'b']
sage: list(_gen_names((1..27)))[-1]
'aa'
"""
import re
from sage.structure.parent_gens import _certify_names
from sage.combinat.words.words import Words
it = iter(Words("abcdefghijklmnopqrstuvwxyz", infinite=False))
it.next() # skip empty word
for x in elts:
name = str(x)
m = re.match('^sqrt\((\d+)\)$', name)
if m:
name = "sqrt%s" % m.groups()[0]
try:
_certify_names([name])
except ValueError:
name = it.next().string_rep()
yield name