On Fri, Feb 13, 2015 at 9:11 PM, Greg Ewing <greg.ewing@canterbury.ac.nz> wrote:

2) The LHS is a complex expression that you only want

...

to write out and evaluate once.

Can you give an example of this? how can put an expression in the right hand side?

myobj.dingle.dell[17] += 42

Hmmm -- I guess I need to look up "expression" -- I would have thought of that as a single object -- but yes, name lookups can be expensive, so there may be a win there. But: In this case, this will only work if myobj.dingle.dell is a mutable object. Even if myobj.dingle.dell[17] is imuttable. but if dell is immutable, it won't work even if dell[17] is mutable. So we don't have the full win here. if += was only supported on mutables, then it would be the other way around. Not sure if there is a clear win there. But maybe it is possible to have a kind of hot fix that allows both. -Chris -- Christopher Barker, Ph.D. Oceanographer Emergency Response Division NOAA/NOS/OR&R (206) 526-6959 voice 7600 Sand Point Way NE (206) 526-6329 fax Seattle, WA 98115 (206) 526-6317 main reception Chris.Barker@noaa.gov