String Index Support for IndexedBy
"Nordlöw" via Digitalmars-d-learn
digitalmars-d-learn at puremagic.com
Wed Apr 15 02:03:55 PDT 2015
On Tuesday, 14 April 2015 at 19:38:10 UTC, Nordlöw wrote:
> I have implemented a type constructor [Ii]ndexedBy at
>
> https://github.com/nordlow/justd/blob/master/typecons_ex.d#L97
>
> restricted by
>
> https://github.com/nordlow/justd/blob/master/typecons_ex.d#L78
>
> See unittests below for usage.
>
> I would now like to extend this to enable a variant usage as
>
> auto xs = x.indexedBy!"I"
>
> I want this to trigger a mixin that defines a
>
> struct I
>
> inside the struct IndexedBy.
>
> But I don't know how to change the definitions of
>
> - isIndexableBy
> - [iI]ndexedBy
>
> in order for this work.
>
> I started by replace all template arguments
>
> I
>
> with
>
> alias I
>
> which I believe is the way to go to make it possible for I to
> either a type or a CT-string. But then I get lots of strange
> compiler messages that I can't figure out what to do with.
>
> Further is my mixin attempt at
>
> https://github.com/nordlow/justd/blob/master/typecons_ex.d#L99
>
> in the right direction. If so do I have to turn IndexedBy into
> a template mixin?
>
> Could someone please help me out here?
I managed to make it all work at
https://github.com/nordlow/justd/blob/master/typecons_ex.d#L114
by using two separate definitions of [Ii]ndexedBy for the cases
where I is either a string literal or a type. This is not ideal
though because it causes code duplication in the two definitions
of IndexedBy. Can anybody come up with an alternate definition of
[Ii]ndexedBy that doesn't required two separated definitions?
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