diff --git a/docs/blog/posts/introducing-absolute-quantities.md b/docs/blog/posts/introducing-absolute-quantities.md index 50a71b85..53009196 100644 --- a/docs/blog/posts/introducing-absolute-quantities.md +++ b/docs/blog/posts/introducing-absolute-quantities.md @@ -248,6 +248,29 @@ assert(point1 == table_top); // quantity point2 = glass1_height - glass1_top;      // no sense - does not compile ``` + +## What about time? + +Everything looks promising and nice for now. But let's look closer into the quantity of time. +There is no way to measure its absolute value as we don't even know where (when?) the time +axis starts... Only time points and time deltas (durations) make sense. + +The above raises a few questions: + +1. Does it mean that `quantity` or `quantity` should not compile? +2. Should we require the user to always state `quantity>` or +   `quantity>`? This would be consistent with physical equations but more + verbose in the source code. +3. Should the syntax `40 * s` be disallowed or should it implicitly create`quantity>` + instead of `quantity`? +4. A somehow similar case might be the length quantity as there is no one well-established + zero origin that serves for all length measurements. However, asking the users always + to provide a `delta` specifier for length would probably be an overkill. + +As you can see, I do not yet have good answers to the above problems yet. Please feel welcome +to share some feedback on this. + + ## New opportunities The new syntax simplifies API as one `quantity` class template will now serve all quantity