On Monday, 17 November 2025 at 14:46:06 UTC, Brother Bill wrote:
In D, they are allowed to mutate parameters which seems to
violate purity. Why did D make this choice and when to best
exploit this architectural decision.
It only violate purity in the sense of how other language define
it, but it makes a lot of sense to be allowed to mutate.
"pure" is a nice idea, the problem start when you want to use it
and a lot of stuff isn't actually marked pure, such as a lot of
core.stdc.math:
https://github.com/dlang/dmd/blob/master/druntime/src/core/stdc/math.d#L2968
Why is atan2f not pure? I have no idea.
Then constructs that could be all pure end up not being marked
pure.
