Re: [PHP-DEV] [RFC] Duration class

On 2026-07-02 05:22, Tim Düsterhus wrote:
> 
> To close this out ourselves: While having a static `sum()` method works 
> for `Duration`s, since the Duration with addition forms an abelian 
> group, this doesn't work for the other future-scope classes where 
> addition doesn't form an (abelian) group. More specifically: Adding two 
> Instants together is not a meaningful operation. Adding a Duration to an 
> Instant however is.
> 
If you want the appropriate mathematical structure, the timeline models 
a one-dimensional real affine space, in which Durations are vectors and 
Instants are points; it's a vector space that has forgotten its origin 
(the choice of epoch is arbitrary and not a distinguished point of the 
space - as evidenced by how many of them there are).