I apologise if I'm making more suggestions that have been discussed in the
past, I'm genuinely searching before I click the compose button and not
finding anything!
I'd like to see this implemented, at least for greater/less than (-or equal
to).
a < b < c
a <= b <= c
Desugars to
a < b && b < c
a <= b && b <= c
For a real-world example
var pos = element.getBoundingClientRect(),
inView = 0 <= pos.left && pos.left <= window.innerWidth && 0 <=
pos.top && pos.top <= window.innerHeight;
Could be rewritten as
var pos = element.getBoundingClientRect(),
inView = 0 <= pos.left <= window.innerWidth && 0 <= pos.top <=
window.innerHeight;
There's a lot to be said for readability, and each operand needs only be
evaluated once, so it could help avoid the need for creating variables to
store the result of a function or a getter (or prevent the need for either
to be invoked more than once).
It's also supported (as the title suggests) by Python [1], Perl 6 [2] and
CoffeeScript [3]. Those languages support chaining the equality operators
too.
It's potentially a breaking change, because
0 < 1 < 1
evaluates to false in current implementations because
(0 < 1) < 1
However, I think we'd be hard pressed to find code like this with
greater/less than or equality operators.
[1] http://docs.python.org/2/reference/expressions.html#not-in
[2] http://en.wikipedia.org/wiki/Perl_6#Chained_comparisons
[3] http://coffeescript.org/#comparisons
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