Is this a bug?

[Grant Edwards]

On 2005-04-25, Robert Kern <rkern at ucsd.edu> wrote:

>> I certainly don't see how.  Strings are immutable.  The old
>> object can't be modified in-place, so the "in-place" behavior
>> is moot.
>
> It's the left-hand-side, in this case a list, that gets modified 
> in-place. Whether the right-hand-side is mutable or not is irrelevant.

You're right.  I had things backwards in my head.

>> Your quote states quite clearly that the binary operation *is
>> the same* whether it's spelt a = a + b or a += b.  That is
>> simply not true for the example we're discussing.
>
> No, the quote says "with the exception of the possible
> in-place behavior, the binary operation performed by augmented
> assignment is the same as the normal binary operations." This
> is "in-place" behavior.  Badly designed "in-place" behavior,
> yes.

Right. The binary operation performed should be the same
regardless of whether it is done in place or not.  In this
case, the "in-place" behavior is completely different than the
other spelling.

> It's a mistake, but it's been in the wild too long to be changed. Thus, 
> it should be documented.

Life's like that, unfortunately.

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