Steven D'Aprano wrote:
On Wed, 18 Mar 2009 12:21:46 am Jacob Holm wrote:
I believe that as soon as the left-hand side stops being a simple variable and it is used in non-trivial expressions on the right-hand side, using the keyword would help clarify the intent. What I mean is that the examples you should be looking at are more like:
A[n+1] = same*same + 1 B[2*j].foo = frobnicate(same, same+1) ...
If you try expanding these into current python with minimal change in semantics you will end up with something like
_1 = n+1 _2 = A[_1] A[_1] = _2*_2 + 1 del _1 del _2
_1 = B[2*j] _2 = _1.foo _1.foo = frobnicate(_2, _2+1) del _1 del _2
which is much less readable.
Of course it is, because it's obfuscated. What's with the leading underscore names? Inside a function, they're not accessible to outside callers, so the notion of "private" and "public" doesn't apply, and in module-level code you delete them at the end, so they won't be imported because they no longer exist. (BTW, there's no need to delete the names one at a time. "del _1, _2" does what you want.)
What's wrong with the clear, simple and obvious?
A[n+1] = A[n+1]**2 + 1
What is wrong is that it computes (n+1) twice, and it uses a different operator to avoid doing the __getitem__ twice. The whole point of the exercise was to get as close as possible to what I think the expression using "same" should mean. I tried to follow the common style for that kind of expansion as seen elsewhere on this list to make that clear. Obviously I failed. Jacob