On 01/12/2016 03:01 PM, John Colvin wrote:
On Tuesday, 12 January 2016 at 19:28:36 UTC, Andrei Alexandrescu wrote:
On 01/12/2016 02:13 PM, John Colvin wrote:
a<=b and b<=a must also be false.
Would the advice "Only use < and == for partially-ordered data" work?
-- Andrei
If by that you mean "Only use <= or >= on data that defines a total
ordering"* I guess it would work, but it has some pretty big downsides:
1) Annoying to use.
2) You have to use the opCmp return 0 (which normally means a[<>]=b &&
b[<>]=a) to mean "not comparable".
3) Not enforceable. Because of 2 you'll always get true if you use >= or
<= on any a pair that doesn't have a defined ordering.
4) inefficient (have to do both < and == separately which can be a lot
more work than <=).
*would be safer to say "types that define", but strictly speaking...
I'd be in favor of giving people the option to disable the use of <= and
>= for specific data. It's a simple and logical approach. -- Andrei
