Re: "undefined behavior"?

On 6/14/2024 11:56 PM, Keith Thompson wrote:

DFS <nospam@dfs.com> writes:

On 6/14/2024 9:39 PM, Keith Thompson wrote:

DFS <nospam@dfs.com> writes:
[...]

During conversion, I got a Python error I don't remember seeing in the past:
>
"TypeError: list indices must be integers or slices, not float"
>
because division returns a float, and some of the array addressing was
like this: nums[i/2].

[...]
C's "/" operator yields a result with the type of the operands
(after
promotion to a common type).
Python's "/" operator yields a floating-point result.  For C-style
integer division, Python uses "//".  (Python 2 is more C-like.)

>
I was surprised python did that, since every division used in the
array addressing results in an integer.
>
After casting i to an int before any array addressing, // works.

 I'm surprised you needed to convert i to an int.  I would think that

 > just replacing nums[i/2] by nums[i//2] would do the trick,
 > as long> as i always has an int value (note Python's dynamic typing).   If i

is acquiring a float value, that's probably a bug, given the name.

I spotted the issue.  Just prior to using i for array addressing I said:
i = N/2.
The fix is set i = int(N/2)

But if you want help with your Python code, comp.lang.python is the
place to ask.

Thanks for your help, but David Brown is a Python developer and I'll ask him python questions here whenever I care to.
In the recent past you were involved in discussions on perl, Fortran and awk, among other off-topics.
Rules for thee but not for me?