xsrange int-overflow

[dkrenn]

for _ in xsrange(Integer(0), Integer(2^63)):
    pass

gives

Traceback (click to the left of this block for traceback)
...
OverflowError: Python int too large to convert to C long

(clearly, the same error raises if Integer is skipped)

[nbruin]

This is a ​documented restriction on xrange and sage's code will only run into it in situations where the full iterator would never be exhausted (implementation uses xrange(icount)). Compare:

sage: for _ in xsrange(Integer(2^63-10), Integer(2^63)): pass #no problem
sage: for _ in xrange(Integer(2^63-10), Integer(2^63)): pass
OverflowError: Python int too large to convert to C long

so the question is really whether xsrange should also be usable to create (effectively) infinite arithmetic progressions. Incidentally, xrange and xsrange model different kinds of objects: xrange implements __getitem__ and __iter__ but not next, so it's really just modelling a finite arithmetic progression as (something close to) a list, whereas xsrange is a generator expression, i.e., an iterator:

sage: xrange(2^63-1)[2^33]
8589934592
sage: xsrange(2^63-1)[2^33]
TypeError: 'generator' object has no attribute '__getitem__'

[jdemeyer]

Duplicate of #20094.