On Sat, Aug 08, 2020 at 08:13:53PM -0400, David Mertz wrote:
> Yes, this is absolutely doable! I guess my argument in several posts is
> that this simple level of analysis of "possible bounds violation" is rarely
> useful (at least in a Python context[*]). Vastly more complicated formal
> proofs might be useful... But, y'know, way more work for tools.
>
> [*] For languages with bounded data types, this is more compelling. If I
> think a variable will *definitely* fit in a uint8, having the static tool
> tell me it might not is powerful.
uint8 = int[0:256]
So if it's useful to know that something might violate the type uint8,
surely it is just as useful to know that it might violate the range
int[0:256].
For what it's worth, I have often had IndexErrors from indexing into a
list or string that were a bugger to debug. But it is one thing to have
a static checker that can tell me if i might exceed the bounds 0...256
and another that can tell me if i might exceed the bounds 0...N where N
is not known until runtime. I suppose this is why bounds checking so
often gets turned into runtime checks, but Python already has that: you
get an IndexError, not a seg fault.
--
Steven
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