Hello,
How likely (based on backward compats) that Harmony will support
Pythonic negative indices for arrays? Ruby supports them too. There was
previous indirect mention, were Brendan agreed that Harmony needs such a
semantics for arrays, however, that discussion wasn't formed to
something concrete.
Recently, there was the same discussion in CoffeeScript's tracker --
https://github.com/jashkenas/coffee-script/issues#issue/827 . Since
Coffee uses JavaScript as its lower level, there were proposals to
provide an alternative syntax for this (e.g. a[* - 1], where * means
a.length, allowing this feature to be generic), though, I'm not sure
this exact syntax is needed for ES. However, I mentioned there, that if
Harmony itself will support this feature in Python's/Ruby's semantics,
then Coffee won't need an alternative thing.
Currently, this feature may be easily implemented using proxies:
https://github.com/DmitrySoshnikov/es-laboratory/blob/master/examples/array-negative-indices.js
(example),
https://github.com/DmitrySoshnikov/es-laboratory/blob/master/src/array-negative-indices.js
(implementation), however possibly it's good to have this semantics for
objects with [[Class]] "Array" as native. I think it's acceptable, since
we already have such alternative semantics for String objects.
Toughs?
Dmitry.
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