On Tuesday, 23 August 2016 at 20:40:06 UTC, Andrei Alexandrescu
wrote:
Currently checkedint
(https://github.com/dlang/phobos/pull/4613) stands at 2432
lines and implements a variety of checking behaviors. At this
point I just figured I can very easily add custom bounds, e.g.
an int limited to 0 through 100 etc. It would take just a few
lines because a lot of support is there (bounds hooks, custom
min/max) anyway.
struct Checkedint(T, Hook = Abort, T min = T.min, T max =
T.max);
For comparion take a look at my solution at:
https://github.com/nordlow/phobos-next/blob/master/src/bound.d
It may answer some of your questions.
The CT-param `exceptional` should be related to your `Hook`.
The solution is currently bloated as it is interleaved with an
Optional implementation and packing logic.
The CT-params `optional`, `exceptional`, `packed` and `signed`
should probably be merged and stored in a Flags-type.
* When assigning a Checked to another, should the limits be
matched statically or checked dynamically?
I'm not sure. I believe the answer lies in the semantic
(real-life) interpretations of the boundeed types. If the ranges
are related to physical boundaries it should probably be checked
at compile-time like we do with units of measurement libraries.
* When composing, do the limits compose meaningfully?
What do you mean with composing? If you're talking about
value-range algebra then take a look at the definitions of
`opBinary`, `min`, `max` and `abs` in my `bound.d`.
I think all of these questions have answers, but I wanted to
gauge the interest in bounded checked integrals. Would the need
for them justify additional complications in the definition?
One other additional use is for Ada-style fixed-length-array
index types. Such a type can be both bounds-checked and
optionally tied to a specific subtype of a fixed-length array.
Such an implementation is `IndexedBy` at
https://github.com/nordlow/phobos-next/blob/master/src/typecons_ex.d#L167
which is currently in use in my trie-container
https://github.com/nordlow/phobos-next/blob/master/src/trie.d
