http://d.puremagic.com/issues/show_bug.cgi?id=10662

           Summary: byLine!(Char, immutable Char) won't compile in git
                    master
           Product: D
           Version: D2
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: normal
          Priority: P2
         Component: Phobos
        AssignedTo: nobody@puremagic.com
        ReportedBy: ntrel-public@yahoo.co.uk


--- Comment #0 from Nick Treleaven <ntrel-public@yahoo.co.uk> 2013-07-17 04:59:51 PDT ---
This won't compile because readln(buf) now requires a mutable buf.

I have a fix ready to submit presently.

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Nick Treleaven <ntrel-public@yahoo.co.uk> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |pull, rejects-valid


--- Comment #1 from Nick Treleaven <ntrel-public@yahoo.co.uk> 2013-07-17 05:16:54 PDT ---
https://github.com/D-Programming-Language/phobos/pull/1418

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monarchdodra@gmail.com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |monarchdodra@gmail.com


--- Comment #2 from monarchdodra@gmail.com 2013-07-17 05:51:14 PDT ---
I question whether or not this is a "rejects valid": byLine explicitly states buffer re-use, so requesting a `ByLine!(immutable Char)` simply is not possible.

That said, I *would* see this as an enhancement, to have a line reader that always returns brand new buffers (in which case the line may or may not be immutable).

EG: By ByDupLine ?

Either that, or we simply keep using
`byLine().map!"a.dup"`
and
`byLine().map!"a.idup"`

That said, a `byDupLine` *is* a bit more user friendly, and helps limit levels of complexity in user code, as well as limits dependency on algorithm.

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--- Comment #3 from monarchdodra@gmail.com 2013-07-17 08:22:26 PDT ---
(In reply to comment #2)
> I question whether or not this is a "rejects valid": byLine explicitly states buffer re-use, so requesting a `ByLine!(immutable Char)` simply is not possible.
> 
> That said, I *would* see this as an enhancement, to have a line reader that always returns brand new buffers (in which case the line may or may not be immutable).
> 
> EG: By ByDupLine ?
> 
> Either that, or we simply keep using
> `byLine().map!"a.dup"`
> and
> `byLine().map!"a.idup"`
> 
> That said, a `byDupLine` *is* a bit more user friendly, and helps limit levels of complexity in user code, as well as limits dependency on algorithm.

In defense of the "ByDupLine" argument, one *BIG* advantage it can provide is that it can guarantee a single dup per front. `byLine().map!"a.dup`, on the other hand will call dup on every call to front.

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--- Comment #4 from Nick Treleaven <ntrel-public@yahoo.co.uk> 2013-07-17 09:48:23 PDT ---
(In reply to comment #2)
> I question whether or not this is a "rejects valid": byLine explicitly states buffer re-use, so requesting a `ByLine!(immutable Char)` simply is not possible.

Where does byLine state that?

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--- Comment #5 from monarchdodra@gmail.com 2013-07-17 15:04:45 PDT ---
(In reply to comment #4)
> (In reply to comment #2)
> > I question whether or not this is a "rejects valid": byLine explicitly states buffer re-use, so requesting a `ByLine!(immutable Char)` simply is not possible.
> 
> Where does byLine state that?

Hum... I guess it doesn't actually state it (my bad). But even if un-documented, it is the "de facto" behavior, and the subject of countless threads on the boards.

If (*if*) we accept that ByLine is designed as a range wrapper to
"readln(_front)", then we should take into account that readln *does* document
buffer re-use...

That's my take on it anyways. I think adding support for this adds little value (IMO), and can only be exploited with a hard to use syntax.

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Nick Treleaven <ntrel-public@yahoo.co.uk> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|rejects-valid               |


--- Comment #6 from Nick Treleaven <ntrel-public@yahoo.co.uk> 2013-07-18 08:08:27 PDT ---
(In reply to comment #2)
> I question whether or not this is a "rejects valid"

I suppose it's arguable, so I've now removed the rejects-valid keyword. (I
think it did work before the readln(buf) change though).

> That said, I *would* see this as an enhancement, to have a line reader that always returns brand new buffers (in which case the line may or may not be immutable).

I have some ideas about other solutions, I will post something to the NG next week. I can't see how fixing this bug would be undesirable, but I agree byLine!(char, immutable char) is awkward syntax (I have an idea how to improve it).

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