On 2012-05-04 01:11, Stewart Gordon wrote:
To sum it up, it can't be done in the general case. The range API
doesn't know or care about the underlying data structure. That's half
the point of it. The underlying data structure might not even exist. An
example is a range used as a file stream, a random number generator or
to lazily generate a mathematical sequence.
Yeah, I know, I know. It's all good in theory but I never found a use
for it in practice and in most cases it's just annoying.
Moreover, what would you want such a function to return if the range is:
- a file stream with a cache
- an array wrapper to loop infinitely through it?
- a concatenation of ranges that may be of different types?
I was mostly thinking when the range originated from a collection. Where
it's actually possible to transfer the range back to the original
collection type.
Moreover, even if there were some "range with an underlying container"
classification, it would be an extra burden on the writer of the range
wrapper to implement this.
No, I was thinking that the developer of the collection would provide
that. I mean, it's already possible to transform a range to an array,
I'm sure it's possible to transform it to a list of some kind as well.
Then we could have this for example:
collA.range.toArray();
collB.range.toList();
What I was asking for was if there is, or could be, a generic interface
for this. Something like:
collA.range.toCollection();
collA.range.toCollection();
If "collA" is an array "toCollection" would transform the range to an
array, just as std.array.array does. If "collB" is a list the range
would be transformed back in to a list.
If you want to generate a range that views a container in a certain way,
and then construct a container of the original type (or indeed any type)
from that range, then create the container and then use a foreach loop
on the range (or a .save of it, if you want to keep the range
afterwards) to put the data into the container.
Stewart.
--
/Jacob Carlborg
