On 05/27/2013 01:36 PM, Diggory wrote:
I gather this has been discussed before and even a potential solution
submitted (https://github.com/D-Programming-Language/phobos/pull/780)
However it was dismissed due to too much existing code being broken.
I'd like to suggest a slightly less severe change which should still fix
the issues with TypeTuple:
https://github.com/D-Programming-Language/phobos/pull/1309
It introduces a new template, StaticTuple which can store any template
parameters. The two templates are exactly equivalent except that
TypeTuple checks that its parameters are actually types, so
StaticTuple!(int, float) == TypeTuple!(int, float).
Reasons for the change:
- Tuples seem to confuse everyone trying to learn D, the inconsistency
in TypeTuples is a big part of that. Naming the new type "StaticTuple"
makes it abundantly clear that the built in "Tuple" type is for storing
multiple values together at runtime while a "StaticTuple" is a similar
construction but for compile time.
It is not that similar, as it automatically expands into any context and
hence does not allow a nested structure.
It then follows directly that
"TypeTuple" is a particular type of "StaticTuple" for dealing with types.
I don't think that having a construct that is restricted to just types
makes a lot of sense.
- The current functionality of using TypeTuples with non-types is
extremely useful and yet completely undocumented. This change means that
if some code expects a StaticTuple we can be safe to assume that passing
it non-types will be fine, and it also opens of the doors for other
specialized versions of StaticTuple such as ExpressionTuple. I have
avoided doing anything other than the most basic addition of StaticTuple
in this pull request as further improvements are a separate issue that
can be dealt with later.
TypeTuple does not implement any functionality. It is an 'identity
function'.
- Unless we plan to stick to the current absurd and confusing naming for
TypeTuple forever, it's better to make the change sooner rather than later.
...
The new name should be an improvement. Certainly shorter.
I (and others) just use:
template Seq(T...){ alias Seq = T; }
As far as I am concerned, this won't change if the new name takes a
substantial amount more space.
