Why do some T.init evaluate to true while others to false?

[Basile B. via Digitalmars-d-learn]

On Thursday, 26 May 2016 at 15:11:50 UTC, Basile B. wrote:
> On Thursday, 26 May 2016 at 14:03:16 UTC, ArturG wrote:
>> [...]

> [...]
> - integral(*): if (i) <=> if (i > 0)

I obviously meant:

- integral(*): if (i) <=> if (i <> 0)

and "<=>" stands for "equivalence"