Motive behind !empty() with front() instead of Optional front()

Piotr Mitana piotr.mitana at gmail.com
Fri Mar 26 08:49:30 UTC 2021


On Wednesday, 24 March 2021 at 19:23:21 UTC, Per Nordlöw wrote:
> What's the motive behinds D's range design choice of needing
>
>     if (!empty)
>     {
>         // use front or back
>     }
>
> instead of having front returning an optional/maybe type with 
> enforced pattern matching?
>
> Lack of builtin Optional type?
>
> Choosing the Optional path would have avoided the need for 
> putting error diagnostics such as
>
> https://github.com/dlang/phobos/commit/9bd2f2ba8ff1124a044560c4e6912a13cb5ac694
>
> in the standard library of such an alternative solution.

Actually changing front() to return optionals would probably 
break many things. However, it could be handy to add a method 
called nullableFront or frontOrNull (and nullableBack or 
backOrNull for bidirectional ranges) to std.range.


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