On 9/1/2010 2:42 AM, Paul Rubin wrote:
Terry Reedy<tjre...@udel.edu> writes:
Does anyone seriously think that an implementation should be rejected
as an implementation if it intellegently did seq[n] lookups in
log2(n)/31 time units for all n (as humans would do), instead of
stupidly taking 1 time unit for all n< 2**31 and rejecting all larger
values (as 32-bit CPython does)?
Er, how can one handle n> 2**31 at all, in 32-bit CPython?
I am not sure of what you mean by 'handle'. Ints (longs in 2.x) are not
limited, but indexes are. 2**31 and bigger are summarily rejected as
impossibly too large, even though they might not actually be so these days.
>>> s=b''
>>> s[1]
Traceback (most recent call last):
File "<pyshell#7>", line 1, in <module>
s[1]
IndexError: index out of range
>>> s[2**32]
Traceback (most recent call last):
File "<pyshell#8>", line 1, in <module>
s[2**32]
IndexError: cannot fit 'int' into an index-sized integer
As far as I know, this is undocumented. In any case, this means that if
it were possible to create a byte array longer than 2**31 on an
otherwise loaded 32-bit linux machine with 2**32 memory, then indexing
the end elements would not be possible, which is to say, O(1) would jump
to O(INF). I do not have such a machine to test whether
big = open('2.01.gigabytes', 'rb').read()
executes or raises an exception. Array size limits are also not documented.
--
Terry Jan Reedy
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