• John Chapman (2/2) Mar 16 2018 I need to write to a range created with outputRangeObject, then
• Jonathan M Davis (13/15) Mar 16 2018 The output range API only supports the put function. That's it. The outp...
• Dukc (6/10) Mar 16 2018 I think it's worth warning that appending on an array may
• Jonathan M Davis (29/39) Mar 17 2018 Appending to a dynamic array doesn't invalidate anything. It just result...
• David Nadlinger (10/12) Mar 17 2018 Could you illustrate your problem a bit further?
• John Chapman (8/13) Mar 17 2018 I'm trying to replace the old std.streams in my app with ranges.
• Paolo Invernizzi (8/16) Mar 18 2018 I suggest you to give a fast read to this [1], reactive streams.

John Chapman <johnch_atms hotmail.com> writes:

I need to write to a range created with outputRangeObject, then 
read from it. Is there a way to convert it to an input range?

Jonathan M Davis <newsgroup.d jmdavisprog.com> writes:

On Friday, March 16, 2018 07:57:04 John Chapman via Digitalmars-d-learn 
wrote:
 I need to write to a range created with outputRangeObject, then
 read from it. Is there a way to convert it to an input range?

The output range API only supports the put function. That's it. The output
range supports no way whatsoever to read data, and it has nothing to do with
the input range API. As such, an output range cannot be generically
converted into an input range, but some specific output ranges could be. For
instance, std.array.Appender is an output range, and you get a dynamic array
out of it, which would be an input range. So, if you have control over what
output range you're dealing with, the simplest would be to just use
Appender. If you don't have control over what output range you're dealing
with, then your options depend on what the type you're dealing with is, but
it won't work with fully generic code.

- Jonathan M Davis

Dukc <ajieskola gmail.com> writes:

On Friday, 16 March 2018 at 08:07:09 UTC, Jonathan M Davis wrote:
 For instance, std.array.Appender is an output range, and you 
 get a dynamic array out of it, which would be an input range. 
 So, if you have control over what output range you're dealing 
 with, the simplest would be to just use Appender.

I think it's worth warning that appending on an array may 
invalidate all copies of it. Meaning that you should not append 
on an array while you're iterating over it, unless iterating by 
the original copy of the array. Note that foreach loop copies the 
range by default. Pass refRange(*array) to foreach instead.

Jonathan M Davis <newsgroup.d jmdavisprog.com> writes:

On Saturday, March 17, 2018 06:58:04 Dukc via Digitalmars-d-learn wrote:
 On Friday, 16 March 2018 at 08:07:09 UTC, Jonathan M Davis wrote:
 For instance, std.array.Appender is an output range, and you
 get a dynamic array out of it, which would be an input range.
 So, if you have control over what output range you're dealing
 with, the simplest would be to just use Appender.

 I think it's worth warning that appending on an array may
 invalidate all copies of it. Meaning that you should not append
 on an array while you're iterating over it, unless iterating by
 the original copy of the array. Note that foreach loop copies the
 range by default. Pass refRange(*array) to foreach instead.

Appending to a dynamic array doesn't invalidate anything. It just results in
a new buffer being allocated and the dynamic array being changed to point to
it instead of the dynamic array does not have enough capacity to append in
place. Any other dynamic arrays which were slices of the previous buffer
still refer to it and are perfectly valid.

Yes, if you want to treat a dynamic array as a reference type, it's not
going to work to simply pass around a dynamic array, because dynamic arrays
are pseudo-reference types and not reference types, and if you want a
reference type, you're going to have to wrap the dynamic array in another
type, but the fact that they're pseudo-reference types does not mean that
anything is invalidated when appending.

Now, doing something like iterating over a dynamic array with a foreach loop
and then appending to it in that same loop means that you're really
operating on two dynamic arrays, because the loop is slices the dynamic
array and is thus iterating over another dynamic array which (at least
initially) refers to the same memory, and the appending that you're doing
won't affect it. So, you do have to be careful about appending while
iterating if you really want to be appending to the same dynamic array that
you're iterating over, but everything involved will be valid regardless. It
just may not have the behavior you want, because the dynamic array has been
sliced.

In any case, based on the OP's question, it was my assumption that they
intended to fully write to the output range and then operate on the results
as on input range, which then has none of the problems associated with
trying to put while you pop. If they want to put while they're popping, then
things get far more complicated, and a dynamic array is probably not the
best solution whether Appender is used or not.

- Jonathan M Davis

David Nadlinger <code klickverbot.at> writes:

On Friday, 16 March 2018 at 07:57:04 UTC, John Chapman wrote:
 I need to write to a range created with outputRangeObject, then 
 read from it. Is there a way to convert it to an input range?

Could you illustrate your problem a bit further?

In the literal sense, converting from an output to an input range 
would require using coroutines (where .empty() blocks until the 
output range has supplied the next element).

However, I suspect what you want to do is to write results from 
the output range to a buffer (e.g. an Appender) first, and after 
that – or possibly every so often in chunks – process the results 
further?

  — David

John Chapman <johnch_atms hotmail.com> writes:

On Saturday, 17 March 2018 at 17:16:40 UTC, David Nadlinger wrote:
 On Friday, 16 March 2018 at 07:57:04 UTC, John Chapman wrote:
 I need to write to a range created with outputRangeObject, 
 then read from it. Is there a way to convert it to an input 
 range?

 Could you illustrate your problem a bit further?

I'm trying to replace the old std.streams in my app with ranges. 
I'm interfacing with a networking library to which I supply a 
callback that when invoked provides the requested data. I write 
that data to an output range, but later on I need to read that 
data from the range too - which of course you can't do.

So what I'm looking for is the range-based equivalent of a 
MemoryStream.

Paolo Invernizzi <paolo.invernizzi gmail.com> writes:

On Saturday, 17 March 2018 at 17:51:50 UTC, John Chapman wrote:

 I'm trying to replace the old std.streams in my app with 
 ranges. I'm interfacing with a networking library to which I 
 supply a callback that when invoked provides the requested 
 data. I write that data to an output range, but later on I need 
 to read that data from the range too - which of course you 
 can't do.

 So what I'm looking for is the range-based equivalent of a 
 MemoryStream.

I suggest you to give a fast read to this [1], reactive streams.
The D implementation [2] uses as a base an output range.

They are pretty good in handling time based series event, it this 
is your usecase...

[1] http://reactivex.io
[2] https://github.com/lempiji/rx

/Paolo