Movement against float.init being nan

[Bastiaan Veelo]

On Saturday, 20 August 2022 at 03:12:43 UTC, Steven Schveighoffer 
wrote:
> In other words, NaN is silent. You can't even `assert(x != 
> double.init)`. You have to use an esoteric function `isNaN` for 
> that.

I had some fun with `isNaN` the other day. We used it to check 
for initialisation in an access function to cache an expensive 
computation. This worked brilliantly until we noticed a 
malfunction in the release version. It took a while until I 
realised that I had given the LDC `fastmath` option to the 
release build, which assumes NaN does not occur, which makes 
`isNaN` misbehave.

What I learned from this is to not use this flag globally, and 
add select attributes to select  functions instead. And instead 
of using NaN I now use `std.typecons.Nullable` to signal a dirty 
cache.

— Bastiaan.