Changed #atEnd primitive - #atEnd vs #next returning nil

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Re: Changed #atEnd primitive - #atEnd vs #next returning nil

alistairgrant
Hi Sven,

On 11 April 2018 at 18:53, Sven Van Caekenberghe <[hidden email]> wrote:
> Something is off (and/or I am getting crazy, probably both).
>
> $ ./pharo --headless Pharo.image eval '(FileStream stdin binary; next: 3)'
> 123
> #[49]
>
> ??
>
> This should return #[49 50 51] AFAIK.

I haven't checked properly, but I can take a guess at this...

The file read primitive in FilePlugin tries to read from stdin 1
character at a time (presumably to get around the line buffering that
is done, but I haven't gone through the history.  At one time I think
it modified the terminal settings, but that code is #if'd out).  For
all other streams it attempts to read the requested number of
characters.

StandardFileStream>>readInto:startingAt:count: assumes that
primitiveFileRead will always attempt to read count bytes, but it
actually only attempts to read 1.

Cheers,
Alistair

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Re: Changed #atEnd primitive - #atEnd vs #next returning nil

Sven Van Caekenberghe-2
Hmm, but why does the following work then ?

$ ./pharo --headless Pharo.image eval '(FileStream stdin next: 3)'
123
'123'

The binary case is an error though, for sure.

And Zn character decoding works on binary streams, while the buffering streams read in blocks.

And it always comes back to 'stdin is handled specially', is that so in C, generally speaking ?

I am still digging though. I will send you some code later on.

> On 11 Apr 2018, at 19:08, Alistair Grant <[hidden email]> wrote:
>
> Hi Sven,
>
> On 11 April 2018 at 18:53, Sven Van Caekenberghe <[hidden email]> wrote:
>> Something is off (and/or I am getting crazy, probably both).
>>
>> $ ./pharo --headless Pharo.image eval '(FileStream stdin binary; next: 3)'
>> 123
>> #[49]
>>
>> ??
>>
>> This should return #[49 50 51] AFAIK.
>
> I haven't checked properly, but I can take a guess at this...
>
> The file read primitive in FilePlugin tries to read from stdin 1
> character at a time (presumably to get around the line buffering that
> is done, but I haven't gone through the history.  At one time I think
> it modified the terminal settings, but that code is #if'd out).  For
> all other streams it attempts to read the requested number of
> characters.
>
> StandardFileStream>>readInto:startingAt:count: assumes that
> primitiveFileRead will always attempt to read count bytes, but it
> actually only attempts to read 1.
>
> Cheers,
> Alistair
>


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Re: Changed #atEnd primitive - #atEnd vs #next returning nil

Nicolas Cellier
In reply to this post by alistairgrant


2018-04-11 19:08 GMT+02:00 Alistair Grant <[hidden email]>:
Hi Sven,

On 11 April 2018 at 18:53, Sven Van Caekenberghe <[hidden email]> wrote:
> Something is off (and/or I am getting crazy, probably both).
>
> $ ./pharo --headless Pharo.image eval '(FileStream stdin binary; next: 3)'
> 123
> #[49]
>
> ??
>
> This should return #[49 50 51] AFAIK.

I haven't checked properly, but I can take a guess at this...

The file read primitive in FilePlugin tries to read from stdin 1
character at a time (presumably to get around the line buffering that
is done, but I haven't gone through the history.  At one time I think
it modified the terminal settings, but that code is #if'd out).  For
all other streams it attempts to read the requested number of
characters.

StandardFileStream>>readInto:startingAt:count: assumes that
primitiveFileRead will always attempt to read count bytes, but it
actually only attempts to read 1.

Cheers,
Alistair


https://github.com/OpenSmalltalk/opensmalltalk-vm/issues/150
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Re: Changed #atEnd primitive - #atEnd vs #next returning nil

Sven Van Caekenberghe-2
In reply to this post by Sven Van Caekenberghe-2
Alistair,

> On 11 Apr 2018, at 19:42, Sven Van Caekenberghe <[hidden email]> wrote:
>
> I will send you some code later on.

Today I arranged for my NeoConsole code (that normally works over a network connection) to work over stdio. Although I am not yet happy with every aspect of the implementation, it does work (using unaltered Zn streams and code). The foll

$ cat /etc/issue
Ubuntu 16.04.4 LTS
$ mkdir pharo7
$ cd pharo7/
$ curl get.pharo.org/70+vm | bash
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100  3036  100  3036    0     0  36799      0 --:--:-- --:--:-- --:--:-- 37024
Downloading the latest 70 Image:
    http://files.pharo.org/get-files/70/pharo.zip
Pharo.image
Downloading the latest pharoVM:
        http://files.pharo.org/get-files/70/pharo-linux-stable.zip
pharo-vm/pharo
Creating starter scripts pharo and pharo-ui
On a 64-bit system? You must enable and install the 32-bit libraries
   Please see http://pharo.org/gnu-linux-installation for detailed instructions
$ ./pharo Pharo.image config http://mc.stfx.eu/Neo ConfigurationOfNeoConsole --install=bleedingEdge
'Installing ConfigurationOfNeoConsole bleedingEdge'

Loading 1-baseline of ConfigurationOfNeoConsole...
Fetched -> Neo-Console-Core-SvenVanCaekenberghe.24 --- http://mc.stfx.eu/Neo --- http://mc.stfx.eu/Neo
Loaded -> Neo-Console-Core-SvenVanCaekenberghe.24 --- http://mc.stfx.eu/Neo --- cache
...finished 1-baseline
$ ./pharo Pharo.image eval NeoConsoleStdio run
Neo Console Pharo-7.0+alpha.build.760.sha.d2734dcabda799803c307365bcd120f92211d34a (32 Bit)
pharo> 1+2

3
pharo> 42 factorial

1405006117752879898543142606244511569936384000000000
pharo> Stdio stdin

StdioStream: #stdin
pharo> ==
self: StdioStream: #stdin
class: StdioStream
file: a File
handle: #[148 213 25 107 160 197 105 247 0 0 0 0 0 0 0 0 0 1 255 1]
forWrite: false
peekBuffer: nil
pharo> show StdioStream>>#atEnd
StdioStream>>#atEnd
atEnd

        ^ file atEnd
pharo> get process.list
Morphic UI Process
Delay Scheduling Process
Low Space Watcher
Input Event Fetcher Process
Idle Process
WeakArray Finalization Process
CommandLine handler process
pharo> quit
Bye!
a NeoConsoleStdio

I know there are many approaches to a REPL, I don't claim mine is best, it is just the one that I have been using for years.

In the above, I do not depend on EOF - just to be clear. The point being that there is no immediate fundamental problem.

But there is something wrong with what is returned by Stdio stdin

Sven



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Re: Changed #atEnd primitive - #atEnd vs #next returning nil

Stephane Ducasse-3
In reply to this post by Denis Kudriashov
On Wed, Apr 11, 2018 at 12:04 PM, Denis Kudriashov <[hidden email]> wrote:
> Hi Alistair.
>
> I don't think anybody is annoyed by you. You are doing really good job. And
> nice thing that you are super patient to continue :)


+100000

>
> What I try to understand is why blocking atEnd is bad?
> Here is code from VMMaker:
>
> [stdin atEnd] whileFalse:
> [| nextChunk |
> stdout nextPutAll: 'squeak> '; flush.
> nextChunk := stdin nextChunkNoTag.
> [nextChunk notEmpty and: [nextChunk first isSeparator]] whileTrue:
> [nextChunk := nextChunk allButFirst].
> Transcript cr; nextPutAll: nextChunk; cr; flush.
> [stdout print: (Compiler evaluate: nextChunk); cr; flush]
> on: Error
> do: [:ex| self logError: ex description inContext: ex signalerContext to:
> stderr]].
> quitOnEof ifTrue:
> [SourceFiles at: 2 put: nil.
> Smalltalk snapshot: false andQuit: true]
>
>
> I am not see why it breaks with blocking #atEnd. Can you explain?
>
> 2018-04-11 11:41 GMT+02:00 Alistair Grant <[hidden email]>:
>>
>> Hi Sven,
>>
>> Oh dear.  I feel as though I'm not getting my concerns across at all
>> well, and I'm pushing hard enough that all I'm going to do is make
>> people annoyed.  So let me try to restate the issue one last time
>> before answering your questions directly.
>>
>> Pharo & Squeak have unwritten rules about stream usage that I suspect
>> have just emerged over time without being designed.
>>
>> If you want to be able to iterate over any stream, and in particular
>> stdin from a terminal (which, as far as I know, is the outlier that
>> causes all the problems) you have to follow these rules:
>>
>> 1.  If the stream is character / byte oriented you have to check for
>> EOF using "stream next == nil".  #atEnd can be used, but you'll still
>> have to do the nil check.
>>
>> 2.  All other streams have to check for EOF (end of stream) using
>> #atEnd.  "stream next == nil" can be used, but you'll still need to
>> test #atEnd to determine whether nil is a value returned by the
>> stream.
>>
>> If you write code that you want to be able to consume characters,
>> bytes or any other object, you'll have to test both "stream next ==
>> nil" and #atEnd.
>>
>> The rules are the result of the original blue book design being that
>> #atEnd should be used, and then character input from a terminal being
>> added later, but always returning an EOF character (nil) before #atEnd
>> answers correctly.
>>
>> At the moment, ZnCharacterEncoder uses #atEnd on character / byte
>> streams, so fails for stdin on a terminal.
>>
>> Back to your questions:
>>
>> On 11 April 2018 at 11:12, Sven Van Caekenberghe <[hidden email]> wrote:
>> >
>> >
>> >> On 11 Apr 2018, at 10:29, Alistair Grant <[hidden email]> wrote:
>> >>
>> >> Hi Denis,
>> >>
>> >> On 11 April 2018 at 10:02, Denis Kudriashov <[hidden email]>
>> >> wrote:
>> >>>
>> >>> 2018-04-11 8:32 GMT+02:00 Alistair Grant <[hidden email]>:
>> >>>>
>> >>>>>>> Where is it being said that #next and/or #atEnd should be blocking
>> >>>>>>> or
>> >>>>>>> non-blocking ?
>> >>>>>>
>> >>>>>> There is existing code that assumes that #atEnd is non-blocking and
>> >>>>>> that #next is allowed block.  I believe that we should keep those
>> >>>>>> conditions.
>> >>>>>
>> >>>>> I fail to see where that is written down, either way. Can you point
>> >>>>> me
>> >>>>> to comments stating that, I would really like to know ?
>> >>>>
>> >>>> I'm not aware of it being written down, just that ever existing
>> >>>> implementation I'm aware of behaves this way.
>> >>>>
>> >>>> On the other hand, making #atEnd blocking breaks Eliot's REPL sample
>> >>>> (in Squeak).
>> >>>
>> >>>
>> >>> Could you write here this example, please?
>> >>
>> >> The code is loaded in squeak using:
>> >>
>> >>
>> >> https://github.com/OpenSmalltalk/opensmalltalk-vm/blob/Cog/image/buildspurtrunkreaderimage.sh
>> >>
>> >> for 32 bit images.  It loads:
>> >>
>> >>
>> >> https://github.com/OpenSmalltalk/opensmalltalk-vm/blob/Cog/image/LoadReader.st
>> >>
>> >> which loads package CogTools-Listener in
>> >> http://source.squeak.org/VMMaker
>> >>
>> >> An image that automatically runs the code and nothing else is created
>> >> in:
>> >>
>> >>
>> >> https://github.com/OpenSmalltalk/opensmalltalk-vm/blob/Cog/image/StartReader.st
>> >>
>> >>
>> >> If you want to run it interactively you can load CogTools-Listener and
>> >> do something like:
>> >>
>> >> StdioListener new
>> >>    quitOnEof: false;
>> >>    run
>> >
>> > What does #quitOnEof: do ? Can the StdioListener code be browsed/viewed
>> > online somewhere ?
>>
>> I just referenced this as an example of making #atEnd (really
>> FilePlugin>>primitiveFileAtEnd) blocking causing problems.  I wasn't
>> expecting people to go and look at the code or use it as a test.
>>
>> If you really want to look at it (from Pharo):
>>
>> 1. Add http://source.squeak.org/VMMaker as a repository.
>> 2. Browse the CogTools-Listener package
>>
>>
>> >> If you modify #atEnd to block it will result in the "squeak>" input
>> >> prompt being printed in the terminal after the input has been entered.
>> >
>> > How does one modify #atEnd to block ? I suppose you are talking about
>> > StdioStream>>#atEnd ?
>>
>> I meant the primitive, i.e. FilePlugin>>primitiveFileAtEnd /
>> FilePluginPrims>>atEnd:.
>>
>>
>> >  ^ self peek isNil
>> >
>> > ?
>> >
>> > PS: I liked your runnable example better, I will try it later on. Thx!
>>
>> Right.  My code is meant to be minimal and trigger the problem I'm
>> actually focused on - that ZnCharacterEncoder doesn't work with stdin
>> from a terminal.
>>
>> Sven has expressed a hesitation to change the internal operation of
>> the Zinc streams from using #atEnd to "stream peek == nil" and this
>> whole discussion is really about us trying to resolve our different
>> perspective of the best path forward.  I respect Sven and his work so
>> I'm trying to justify the change (but I'm not expressing it at all
>> well, obviously).
>>
>> Cheers,
>> Alistair
>>
>>
>>
>> >> The code can be loaded in to Pharo and basically works, but the output
>> >> tends to be hidden behind the next input prompt because it uses #cr
>> >> instead of #lf.  You can easily modify StdioListener>>initialize to
>> >> set the line end convention in stdout.
>> >>
>> >> NOTE: It is not intended to be a release quality implementation of a
>> >> evaluation loop.  The whole purpose as I understand it is for it to be
>> >> as simple as possible to assist in tracking down issues using the VM
>> >> simulator.  It runs minimal code to get to the point of waiting for
>> >> user input and then allows an expression that causes problems to be
>> >> entered and traced using the simulator.
>> >>
>> >> Cheers,
>> >> Alistair
>> >>
>> >>
>> >>
>> >>>>>>> How is this related to how EOF is signalled ?
>> >>>>>>
>> >>>>>> Because, combined with terminal EOF not being known until the user
>> >>>>>> explicitly flags it (with Ctrl-D) it means that #atEnd can't be
>> >>>>>> used
>> >>>>>> for iterating over input from stdin connected to a terminal.
>> >>>>>
>> >>>>> This seems to me like an exception that only holds for one
>> >>>>> particular
>> >>>>> stream in one particular scenario (interactive stdin). I might be
>> >>>>> wrong.
>> >>>>>
>> >>>>>>> It seems to me that there are quite a few classes of streams that
>> >>>>>>> are
>> >>>>>>> 'special' in the sense that #next could be blocking and/or #atEnd
>> >>>>>>> could be
>> >>>>>>> unclear - socket/network streams, serial streams, maybe stdio
>> >>>>>>> (interactive
>> >>>>>>> or not). Without a message like #isDataAvailable you cannot handle
>> >>>>>>> those
>> >>>>>>> without blocking.
>> >>>>>>
>> >>>>>> Right.  I think this is a distraction (I was trying to explain some
>> >>>>>> details, but it's causing more confusion instead of helping).
>> >>>>>>
>> >>>>>> The important point is that #atEnd doesn't work for iterating over
>> >>>>>> streams with terminal input
>> >>>>>
>> >>>>> Maybe you should also point to the actual code that fails. I mean
>> >>>>> you
>> >>>>> showed a partial stack trace, but not how you got there, precisely.
>> >>>>> How does
>> >>>>> the application reading from an interactive stdin do to get into
>> >>>>> trouble ?
>> >>>>
>> >>>> Included below.
>> >>>>
>> >>>>
>> >>>>>>> Reading from stdin seems like a very rare case for a Smalltalk
>> >>>>>>> system
>> >>>>>>> (not that it should not be possible).
>> >>>>>>
>> >>>>>> There's been quite a bit of discussion and several projects
>> >>>>>> recently
>> >>>>>> related to using pharo for scripting, so it may become more common.
>> >>>>>> E.g.
>> >>>>>>
>> >>>>>>
>> >>>>>>
>> >>>>>> https://www.quora.com/Can-Smalltalk-be-a-batch-file-scripting-language/answer/Philippe-Back-1?share=c19bfc95
>> >>>>>> https://github.com/rajula96reddy/pharo-cli
>> >>>>>
>> >>>>> Still, it is not common at all.
>> >>>>>
>> >>>>>>> I have a feeling that too much functionality is being pushed into
>> >>>>>>> too
>> >>>>>>> small an API.
>> >>>>>>
>> >>>>>> This is just about how should Zinc streams be iterating over the
>> >>>>>> underlying streams.  You didn't like checking the result of #next
>> >>>>>> for
>> >>>>>> nil since it isn't general, correctly pointing out that nil is a
>> >>>>>> valid
>> >>>>>> value for non-byte oriented streams.  But #atEnd doesn't work for
>> >>>>>> stdin from a terminal.
>> >>>>>>
>> >>>>>>
>> >>>>>> At this point I think there are three options:
>> >>>>>>
>> >>>>>> 1. Modify Zinc to check the return value of #next instead of using
>> >>>>>> #atEnd.
>> >>>>>>
>> >>>>>> This is what all existing character / byte oriented streams in
>> >>>>>> Squeak
>> >>>>>> and Pharo do.  At that point the Zinc streams can be used on all
>> >>>>>> file
>> >>>>>> / stdio input and output.
>> >>>>>
>> >>>>> I agree that such code exists in many places, but there is lots of
>> >>>>> stream reading that does not check for nils.
>> >>>>
>> >>>> Right.  Streams can be categorised in many ways, but for this
>> >>>> discussion I think streams are broken in to two types:
>> >>>>
>> >>>> 1) Byte / Character oriented
>> >>>> 2) All others
>> >>>>
>> >>>> For historical reasons, byte / character oriented streams need to
>> >>>> check for EOF by using "stream next == nil" and all other streams
>> >>>> should use #atEnd.
>> >>>>
>> >>>> This avoids the "nil being part of the domain" issue that was
>> >>>> discussed earlier in the thread.
>> >>>>
>> >>>>
>> >>>>>> 2. Modify all streams to signal EOF in some other way, i.e. a
>> >>>>>> sentinel
>> >>>>>> or notification / exception.
>> >>>>>>
>> >>>>>> This is what we were discussing below.  But it is a decent chunk of
>> >>>>>> work with significant impact on the existing code base.
>> >>>>>
>> >>>>> Agreed. This would be a future extension.
>> >>>>>
>> >>>>>> 3. Require anyone who wants to read from stdin to code around
>> >>>>>> Zinc's
>> >>>>>> inability to handle terminal input.
>> >>>>>>
>> >>>>>> I'd prefer to avoid this option if possible.
>> >>>>>
>> >>>>> See higher for a more concrete usage example request.
>> >>>>
>> >>>>
>> >>>> testAtEnd.st
>> >>>> --
>> >>>> | ch stream string stdin |
>> >>>>
>> >>>> 'stdio.cs' asFileReference fileIn.
>> >>>> "stdin := FileStream stdin."
>> >>>> stdin := ZnCharacterReadStream on:
>> >>>>    (ZnBufferedReadStream on:
>> >>>>        Stdio stdin).
>> >>>> stream := (String new: 100) writeStream.
>> >>>> ch := stdin next.
>> >>>> [ ch == nil ] whileFalse: [
>> >>>>    stream nextPut: ch.
>> >>>>    ch := stdin next. ].
>> >>>> string := stream contents.
>> >>>> FileStream stdout
>> >>>>    nextPutAll: string; lf;
>> >>>>    nextPutAll: 'Characters read: ';
>> >>>>    nextPutAll: string size asString;
>> >>>>    lf.
>> >>>> Smalltalk snapshot: false andQuit: true.
>> >>>> --
>> >>>>
>> >>>> Execute with:
>> >>>>
>> >>>> ./pharo --headless Pharo7.0-64bit-e76f1a2.image testAtEnd.st
>> >>>>
>> >>>> and type Ctrl-D gives:
>> >>>>
>> >>>>
>> >>>> 'Errors in script loaded from testAtEnd.st'
>> >>>> MessageNotUnderstood: receiver of "<" is nil
>> >>>> UndefinedObject(Object)>>doesNotUnderstand: #<
>> >>>> ZnUTF8Encoder>>nextCodePointFromStream:
>> >>>> ZnUTF8Encoder(ZnCharacterEncoder)>>nextFromStream:
>> >>>> ZnCharacterReadStream>>nextElement
>> >>>> ZnCharacterReadStream(ZnEncodedReadStream)>>next
>> >>>> UndefinedObject>>DoIt
>> >>>> OpalCompiler>>evaluate
>> >>>>
>> >>>>
>> >>>> Using #atEnd to control the loop instead of "stdin next == nil"
>> >>>> produces the same result.
>> >>>>
>> >>>> Replacing stdin with FileStream stdin makes the script work.
>> >>>>
>> >>>> stdio.cs fixes a bug in StdioStream which really isn't part of this
>> >>>> discussion (PR to be submitted).
>> >>>>
>> >>>> Cheers,
>> >>>> Alistair
>> >>>>
>> >>>>
>> >>>>
>> >>>>
>> >>>>>> Does that clarify the situation?
>> >>>>>
>> >>>>> Yes, it helps. Thanks. But questions remain.
>> >>>>>
>> >>>>>> Thanks,
>> >>>>>> Alistair
>> >>>>>>
>> >>>>>>
>> >>>>>>
>> >>>>>>>> On 10 Apr 2018, at 18:30, Alistair Grant <[hidden email]>
>> >>>>>>>> wrote:
>> >>>>>>>>
>> >>>>>>>> First a quick update:
>> >>>>>>>>
>> >>>>>>>> After doing some work on primitiveFileAtEnd, #atEnd now answers
>> >>>>>>>> correctly for files that don't report their size correctly, e.g.
>> >>>>>>>> /dev/urandom and /proc/cpuinfo, whether the files are opened
>> >>>>>>>> directly
>> >>>>>>>> or
>> >>>>>>>> redirected through stdin.
>> >>>>>>>>
>> >>>>>>>> However determining whether stdin from a terminal has reached the
>> >>>>>>>> end
>> >>>>>>>> of
>> >>>>>>>> file can't be done without making #atEnd blocking since we have
>> >>>>>>>> to
>> >>>>>>>> wait
>> >>>>>>>> for the user to flag the end of file, e.g. by typing Ctrl-D.  And
>> >>>>>>>> #atEnd
>> >>>>>>>> is assumed to be non-blocking.
>> >>>>>>>>
>> >>>>>>>> So currently using ZnCharacterReadStream with stdin from a
>> >>>>>>>> terminal
>> >>>>>>>> will
>> >>>>>>>> result in a stack dump similar to:
>> >>>>>>>>
>> >>>>>>>> MessageNotUnderstood: receiver of "<" is nil
>> >>>>>>>> UndefinedObject(Object)>>doesNotUnderstand: #<
>> >>>>>>>> ZnUTF8Encoder>>nextCodePointFromStream:
>> >>>>>>>> ZnUTF8Encoder(ZnCharacterEncoder)>>nextFromStream:
>> >>>>>>>> ZnCharacterReadStream>>nextElement
>> >>>>>>>> ZnCharacterReadStream(ZnEncodedReadStream)>>next
>> >>>>>>>> UndefinedObject>>DoIt
>> >>>>>>>>
>> >>>>>>>>
>> >>>>>>>> Going back through the various suggestions that have been made
>> >>>>>>>> regarding
>> >>>>>>>> using a sentinel object vs. raising a notification / exception,
>> >>>>>>>> my
>> >>>>>>>> (still to be polished) suggestion is to:
>> >>>>>>>>
>> >>>>>>>> 1. Add an endOfStream instance variable
>> >>>>>>>> 2. When the end of the stream is reached answer the value of the
>> >>>>>>>> instance variable (i.e. the result of sending #value to the
>> >>>>>>>> variable).
>> >>>>>>>> 3. The initial default value would be a block that raises a
>> >>>>>>>> Deprecation
>> >>>>>>>> warning and then returns nil.  This would allow existing code to
>> >>>>>>>> function for a changeover period.
>> >>>>>>>> 4. At the end of the deprecation period the default value would
>> >>>>>>>> be
>> >>>>>>>> changed to a unique sentinel object which would answer itself as
>> >>>>>>>> its
>> >>>>>>>> #value.
>> >>>>>>>>
>> >>>>>>>> At any time users of the stream can set their own sentinel,
>> >>>>>>>> including
>> >>>>>>>> a
>> >>>>>>>> block that raises an exception.
>> >>>>>>>>
>> >>>>>>>>
>> >>>>>>>> Cheers,
>> >>>>>>>> Alistair
>> >>>>>>>>
>> >>>>>>>>
>> >>>>>>>> On 4 April 2018 at 19:24, Stephane Ducasse
>> >>>>>>>> <[hidden email]>
>> >>>>>>>> wrote:
>> >>>>>>>>> Thanks for this discussion.
>> >>>>>>>>>
>> >>>>>>>>> On Wed, Apr 4, 2018 at 1:37 PM, Sven Van Caekenberghe
>> >>>>>>>>> <[hidden email]>
>> >>>>>>>>> wrote:
>> >>>>>>>>>> Alistair,
>> >>>>>>>>>>
>> >>>>>>>>>> First off, thanks for the discussions and your contributions, I
>> >>>>>>>>>> really appreciate them.
>> >>>>>>>>>>
>> >>>>>>>>>> But I want to have a discussion at the high level of the
>> >>>>>>>>>> definition
>> >>>>>>>>>> and semantics of the stream API in Pharo.
>> >>>>>>>>>>
>> >>>>>>>>>>> On 4 Apr 2018, at 13:20, Alistair Grant
>> >>>>>>>>>>> <[hidden email]>
>> >>>>>>>>>>> wrote:
>> >>>>>>>>>>>
>> >>>>>>>>>>> On 4 April 2018 at 12:56, Sven Van Caekenberghe <[hidden email]>
>> >>>>>>>>>>> wrote:
>> >>>>>>>>>>>> Playing a bit devil's advocate, the idea is that, in general,
>> >>>>>>>>>>>>
>> >>>>>>>>>>>> [ stream atEnd] whileFalse: [ stream next. "..." ].
>> >>>>>>>>>>>>
>> >>>>>>>>>>>> is no longer allowed ?
>> >>>>>>>>>>>
>> >>>>>>>>>>> It hasn't been allowed "forever" [1].  It's just been misused
>> >>>>>>>>>>> for
>> >>>>>>>>>>> almost as long.
>> >>>>>>>>>>>
>> >>>>>>>>>>> [1] Time began when stdio stream support was introduced. :-)
>> >>>>>>>>>>
>> >>>>>>>>>> I am still not convinced. Another way to put it would be that
>> >>>>>>>>>> the
>> >>>>>>>>>> old #atEnd or #upToEnd do not make sense for these streams and
>> >>>>>>>>>> some new loop
>> >>>>>>>>>> is needed, based on a new test (it exists for socket streams
>> >>>>>>>>>> already).
>> >>>>>>>>>>
>> >>>>>>>>>> [ stream isDataAvailable ] whileTrue: [ stream next ]
>> >>>>>>>>>>
>> >>>>>>>>>>>> And you want to replace it with
>> >>>>>>>>>>>>
>> >>>>>>>>>>>> [ stream next ifNil: [ false ] ifNotNil: [ :x | "..." true ]
>> >>>>>>>>>>>> whileTrue.
>> >>>>>>>>>>>>
>> >>>>>>>>>>>> That is a pretty big change, no ?
>> >>>>>>>>>>>
>> >>>>>>>>>>> That's the way quite a bit of code already operates.
>> >>>>>>>>>>>
>> >>>>>>>>>>> As Denis pointed out, it's obviously problematic in the
>> >>>>>>>>>>> general
>> >>>>>>>>>>> sense,
>> >>>>>>>>>>> since nil can be embedded in non-byte oriented streams.  I
>> >>>>>>>>>>> suspect
>> >>>>>>>>>>> that in practice not many people write code that reads streams
>> >>>>>>>>>>> from
>> >>>>>>>>>>> both byte oriented and non-byte oriented streams.
>> >>>>>>>>>>
>> >>>>>>>>>> Maybe yes, maybe no. As Denis' example shows there is a clear
>> >>>>>>>>>> definition problem.
>> >>>>>>>>>>
>> >>>>>>>>>> And I do use streams of byte arrays or strings all the time,
>> >>>>>>>>>> this
>> >>>>>>>>>> is really important. I want my parsers to work on all kinds of
>> >>>>>>>>>> streams.
>> >>>>>>>>>>
>> >>>>>>>>>>>> I think/feel like a proper EOF exception would be better,
>> >>>>>>>>>>>> more
>> >>>>>>>>>>>> correct.
>> >>>>>>>>>>>>
>> >>>>>>>>>>>> [ [ stream next. "..." true ] on: EOF do: [ false ] ]
>> >>>>>>>>>>>> whileTrue.
>> >>>>>>>>>>>
>> >>>>>>>>>>> I agree, but the email thread Nicolas pointed to raises some
>> >>>>>>>>>>> performance questions about this approach.  It should be
>> >>>>>>>>>>> straightforward to do a basic performance comparison which
>> >>>>>>>>>>> I'll
>> >>>>>>>>>>> get
>> >>>>>>>>>>> around to if other objections aren't raised.
>> >>>>>>>>>>
>> >>>>>>>>>> Reading in bigger blocks, using #readInto:startingAt:count:
>> >>>>>>>>>> (which
>> >>>>>>>>>> is basically Unix's (2) Read sys call), would solve performance
>> >>>>>>>>>> problems, I
>> >>>>>>>>>> think.
>> >>>>>>>>>>
>> >>>>>>>>>>>> Will we throw away #atEnd then ? Do we need it if we cannot
>> >>>>>>>>>>>> use
>> >>>>>>>>>>>> it ?
>> >>>>>>>>>>>
>> >>>>>>>>>>> Unix file i/o returns EOF if the end of file has been reach OR
>> >>>>>>>>>>> if
>> >>>>>>>>>>> an
>> >>>>>>>>>>> error occurs.  You should still check #atEnd after reading
>> >>>>>>>>>>> past
>> >>>>>>>>>>> the
>> >>>>>>>>>>> end of the file to make sure no error occurred.  Another part
>> >>>>>>>>>>> of
>> >>>>>>>>>>> the
>> >>>>>>>>>>> primitive change I'm proposing is to return additional
>> >>>>>>>>>>> information
>> >>>>>>>>>>> about what went wrong in the event of an error.
>> >>>>>>>>>>
>> >>>>>>>>>> I am sorry, but this kind of semantics (the OR) is way too
>> >>>>>>>>>> complex
>> >>>>>>>>>> at the general image level, it is too specific and based on
>> >>>>>>>>>> certain
>> >>>>>>>>>> underlying implementation details.
>> >>>>>>>>>>
>> >>>>>>>>>> Sven
>> >>>>>>>>>>
>> >>>>>>>>>>> We could modify the read primitive so that it fails if an
>> >>>>>>>>>>> error
>> >>>>>>>>>>> has
>> >>>>>>>>>>> occurred, and then #atEnd wouldn't be required.
>> >>>>>>>>>>>
>> >>>>>>>>>>> Cheers,
>> >>>>>>>>>>> Alistair
>> >>>>>>>>>>>
>> >>>>>>>>>>>
>> >>>>>>>>>>>
>> >>>>>>>>>>>>> On 4 Apr 2018, at 12:41, Alistair Grant
>> >>>>>>>>>>>>> <[hidden email]>
>> >>>>>>>>>>>>> wrote:
>> >>>>>>>>>>>>>
>> >>>>>>>>>>>>> Hi Nicolas,
>> >>>>>>>>>>>>>
>> >>>>>>>>>>>>> On 4 April 2018 at 12:36, Nicolas Cellier
>> >>>>>>>>>>>>> <[hidden email]> wrote:
>> >>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>
>> >>>>>>>>>>>>>> 2018-04-04 12:18 GMT+02:00 Alistair Grant
>> >>>>>>>>>>>>>> <[hidden email]>:
>> >>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>> Hi Sven,
>> >>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>> On Wed, Apr 04, 2018 at 11:32:02AM +0200, Sven Van
>> >>>>>>>>>>>>>>> Caekenberghe wrote:
>> >>>>>>>>>>>>>>>> Somehow, somewhere there was a change to the
>> >>>>>>>>>>>>>>>> implementation
>> >>>>>>>>>>>>>>>> of the
>> >>>>>>>>>>>>>>>> primitive called by some streams' #atEnd.
>> >>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>> That's a proposed change by me, but it hasn't been
>> >>>>>>>>>>>>>>> integrated
>> >>>>>>>>>>>>>>> yet.  So
>> >>>>>>>>>>>>>>> the discussion below should apply to the current stable vm
>> >>>>>>>>>>>>>>> (from August
>> >>>>>>>>>>>>>>> last year).
>> >>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>> IIRC, someone said it is implemented as 'remaining size
>> >>>>>>>>>>>>>>>> being
>> >>>>>>>>>>>>>>>> zero'
>> >>>>>>>>>>>>>>>> and some virtual unix files like /dev/random are zero
>> >>>>>>>>>>>>>>>> sized.
>> >>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>> Currently, for files other than sdio (stdout, stderr,
>> >>>>>>>>>>>>>>> stdin)
>> >>>>>>>>>>>>>>> it is
>> >>>>>>>>>>>>>>> effectively defined as:
>> >>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>> atEnd := stream position >= stream size
>> >>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>> And, as you say, plenty of virtual unix files report size
>> >>>>>>>>>>>>>>> 0.
>> >>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>> Now, all kinds of changes are being done image size to
>> >>>>>>>>>>>>>>>> work
>> >>>>>>>>>>>>>>>> around this.
>> >>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>> I would phrase this slightly differently :-)
>> >>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>> Some code does the right thing, while other code doesn't.
>> >>>>>>>>>>>>>>> E.g.:
>> >>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>> MultiByteFileStream>>upToEnd is good, while
>> >>>>>>>>>>>>>>> FileStream>>contents is incorrect
>> >>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>> I am a strong believer in simple, real (i.e. infinite)
>> >>>>>>>>>>>>>>>> streams, but I
>> >>>>>>>>>>>>>>>> am not sure we are doing the right thing here.
>> >>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>> Point is, I am not sure #next returning nil is official
>> >>>>>>>>>>>>>>>> and
>> >>>>>>>>>>>>>>>> universal.
>> >>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>> Consider the comments:
>> >>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>> Stream>>#next
>> >>>>>>>>>>>>>>>> "Answer the next object accessible by the receiver."
>> >>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>> ReadStream>>#next
>> >>>>>>>>>>>>>>>> "Primitive. Answer the next object in the Stream
>> >>>>>>>>>>>>>>>> represented
>> >>>>>>>>>>>>>>>> by the
>> >>>>>>>>>>>>>>>> receiver. Fail if the collection of this stream is not an
>> >>>>>>>>>>>>>>>> Array or a
>> >>>>>>>>>>>>>>>> String.
>> >>>>>>>>>>>>>>>> Fail if the stream is positioned at its end, or if the
>> >>>>>>>>>>>>>>>> position is out
>> >>>>>>>>>>>>>>>> of
>> >>>>>>>>>>>>>>>> bounds in the collection. Optional. See Object
>> >>>>>>>>>>>>>>>> documentation
>> >>>>>>>>>>>>>>>> whatIsAPrimitive."
>> >>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>> Note how there is no talk about returning nil !
>> >>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>> I think we should discuss about this first.
>> >>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>> Was the low level change really correct and the right
>> >>>>>>>>>>>>>>>> thing
>> >>>>>>>>>>>>>>>> to do ?
>> >>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>> The primitive change proposed doesn't affect this
>> >>>>>>>>>>>>>>> discussion.
>> >>>>>>>>>>>>>>> It will
>> >>>>>>>>>>>>>>> mean that #atEnd returns false (correctly) sometimes,
>> >>>>>>>>>>>>>>> while
>> >>>>>>>>>>>>>>> currently it
>> >>>>>>>>>>>>>>> returns true (incorrectly).  The end result is still
>> >>>>>>>>>>>>>>> incorrect, e.g.
>> >>>>>>>>>>>>>>> #contents returns an empty string for /proc/cpuinfo.
>> >>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>> You're correct about no mention of nil, but we have:
>> >>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>> FileStream>>next
>> >>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>    (position >= readLimit and: [self atEnd])
>> >>>>>>>>>>>>>>>            ifTrue: [^nil]
>> >>>>>>>>>>>>>>>            ifFalse: [^collection at: (position := position
>> >>>>>>>>>>>>>>> +
>> >>>>>>>>>>>>>>> 1)]
>> >>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>> which has been around for a long time (I suspect, before
>> >>>>>>>>>>>>>>> Pharo
>> >>>>>>>>>>>>>>> existed).
>> >>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>> Having said that, I think that raising an exception is a
>> >>>>>>>>>>>>>>> better
>> >>>>>>>>>>>>>>> solution, but it is a much, much bigger change than the
>> >>>>>>>>>>>>>>> one I
>> >>>>>>>>>>>>>>> proposed
>> >>>>>>>>>>>>>>> in https://github.com/pharo-project/pharo/pull/1180.
>> >>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>> Cheers,
>> >>>>>>>>>>>>>>> Alistair
>> >>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>
>> >>>>>>>>>>>>>> Hi,
>> >>>>>>>>>>>>>> yes, if you are after universal behavior englobing Unix
>> >>>>>>>>>>>>>> streams, the
>> >>>>>>>>>>>>>> Exception might be the best way.
>> >>>>>>>>>>>>>> Because on special stream you can't allways say in advance,
>> >>>>>>>>>>>>>> you
>> >>>>>>>>>>>>>> have to try.
>> >>>>>>>>>>>>>> That's the solution adopted by authors of Xtreams.
>> >>>>>>>>>>>>>> But there is a runtime penalty associated to it.
>> >>>>>>>>>>>>>>
>> >>>>>>>>>>>>>> The penalty once was so high that my proposal to generalize
>> >>>>>>>>>>>>>> EndOfStream
>> >>>>>>>>>>>>>> usage was rejected a few years ago by AndreaRaab.
>> >>>>>>>>>>>>>> http://forum.world.st/EndOfStream-unused-td68806.html
>> >>>>>>>>>>>>>
>> >>>>>>>>>>>>> Thanks for this, I'll definitely take a look.
>> >>>>>>>>>>>>>
>> >>>>>>>>>>>>> Do you have a sense of how Denis' suggestion of using an
>> >>>>>>>>>>>>> EndOfStream
>> >>>>>>>>>>>>> object would compare?
>> >>>>>>>>>>>>>
>> >>>>>>>>>>>>> It would keep the same coding style, but avoid the problems
>> >>>>>>>>>>>>> with
>> >>>>>>>>>>>>> nil.
>> >>>>>>>>>>>>>
>> >>>>>>>>>>>>> Thanks,
>> >>>>>>>>>>>>> Alistair
>> >>>>>>>>>>>>>
>> >>>>>>>>>>>>>
>> >>>>>>>>>>>>>
>> >>>>>>>>>>>>>> I have regularly benched Xtreams, but stopped a few years
>> >>>>>>>>>>>>>> ago.
>> >>>>>>>>>>>>>> Maybe i can excavate and pass on newer VM.
>> >>>>>>>>>>>>>>
>> >>>>>>>>>>>>>> In the mean time, i had experimented a programmable end of
>> >>>>>>>>>>>>>> stream behavior
>> >>>>>>>>>>>>>> (via a block, or any other valuable)
>> >>>>>>>>>>>>>> http://www.squeaksource.com/XTream.htm
>> >>>>>>>>>>>>>> so as to reconcile performance and universality, but it was
>> >>>>>>>>>>>>>> a
>> >>>>>>>>>>>>>> source of
>> >>>>>>>>>>>>>> complexification at implementation side.
>> >>>>>>>>>>>>>>
>> >>>>>>>>>>>>>> Nicolas
>> >>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>> Note also that a Guille introduced something new, #closed
>> >>>>>>>>>>>>>>>> which is
>> >>>>>>>>>>>>>>>> related to the difference between having no more elements
>> >>>>>>>>>>>>>>>> (maybe right now,
>> >>>>>>>>>>>>>>>> like an open network stream) and never ever being able to
>> >>>>>>>>>>>>>>>> produce more data.
>> >>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>> Sven
>> >>>>>>>>>>>>
>> >>>>>>>>>>>>
>> >>>>>>>>>>>
>> >>>>>>>>>>
>> >>>>>>>>>>
>> >>>>>>>>>
>> >>>>>>>>
>> >>>>>>>
>> >>>>>>>
>> >>>>>> <stdio.cs>
>> >
>> >
>>
>

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Re: Changed #atEnd primitive - #atEnd vs #next returning nil

Stephane Ducasse-3
In reply to this post by Sven Van Caekenberghe-2
On Wed, Apr 11, 2018 at 5:33 PM, Sven Van Caekenberghe <[hidden email]> wrote:
> I think we have to reset this whole discussion.
>
>   FileStream stdin
>
> and
>
>   Stdio stdin
>
> are completely different !

Could you explain the difference because I'm dead tired and got confused :)

>
> We'll have to check that first, before talking about the issues raised in this thread.
>
> And BTW these terminal streams are a real pain to test ;-)
>
>> On 11 Apr 2018, at 17:20, Sven Van Caekenberghe <[hidden email]> wrote:
>>
>>
>>
>>> On 11 Apr 2018, at 17:16, Denis Kudriashov <[hidden email]> wrote:
>>>
>>>
>>> 2018-04-11 17:02 GMT+02:00 Sven Van Caekenberghe <[hidden email]>:
>>>
>>>
>>>> On 11 Apr 2018, at 16:36, Sven Van Caekenberghe <[hidden email]> wrote:
>>>>
>>>> I can make your example, using the Zn variants, work with the following change:
>>>>
>>>> StdioStream>>#atEnd
>>>> ^ peekBuffer isNil or: [ (peekBuffer := self next) isNil ]
>>>
>>> Argh, make that
>>>
>>> atEnd
>>>  ^ peekBuffer isNil and: [ (peekBuffer := self next) isNil ]
>>>
>>> But discussion exactly about "self next isNil": how to avoid it.
>>
>> I know, but like this it could/might become an implementation detail.
>>
>> The more things that I try, the more that I feel that stdin is so special that it does not fit in the rest of the stream zoo.
>>
>>> but I am still testing, this is probably not the final answer/solution.
>>>
>>>> Which is a literal implementation of your statement that you can only know that you are atEnd by reading (and thus waiting/blocking) and checking for nil, which seems logical to me, given the fact that you *are* waiting for user input.
>>>>
>>>> BTW, at least on macOS you have to enter ctrl-D (^D) on a separate line, I am not sure how relevant that is, but that is probably another argument that stdin is special (being line-buffered by the OS, EOF needing to be on a separate line).
>>>>
>>>> And FWIW, I have been writing networking code in Pharo for years, and I have never had issues with unclear semantics of these primitives (#atEnd, #next, #peek) on network streams, either the classic SocketStream or the Zdc* streams (TLS or not). That is why I think we have to be careful.
>>>>
>>>> That being said, it is important to continue this discussion, I find it very interesting. I am trying to write some test code using stdin myself, to better understand the topic.
>>>>
>>>>> On 11 Apr 2018, at 16:06, Alistair Grant <[hidden email]> wrote:
>>>>>
>>>>> On 11 April 2018 at 15:11, Sven Van Caekenberghe <[hidden email]> wrote:
>>>>>>
>>>>>>
>>>>>>> On 11 Apr 2018, at 11:12, Sven Van Caekenberghe <[hidden email]> wrote:
>>>>>>>
>>>>>>> How does one modify #atEnd to block ? I suppose you are talking about StdioStream>>#atEnd ?
>>>>>>>
>>>>>>> ^ self peek isNil
>>>>>>>
>>>>>>> ?
>>>>>>
>>>>>> Still the same question, how do you implement a blocking #atEnd for stdin ?
>>>>>>
>>>>>> I have seen your stdio.cs which is indeed needed as the current StdioStream>>#atEnd is bogus for sure.
>>>>>>
>>>>>> But that is still a non-blocking one, right ?
>>>>>>
>>>>>> Since there is a peekBuffer in StdioStream, why can't that be used ?
>>>>>
>>>>> I think you've created a chicken-and-egg problem with this question,
>>>>> but ignoring that for now:
>>>>>
>>>>>
>>>>> StdioStream>>peek
>>>>> "Answer what would be returned if the message next were sent to the
>>>>> receiver. If the receiver is at the end, answer nil.  "
>>>>>
>>>>>  self atEnd ifTrue: [^ nil ].
>>>>>
>>>>>  peekBuffer ifNotNil: [ ^ peekBuffer ].
>>>>>
>>>>>  ^ peekBuffer := self next.
>>>>>
>>>>>
>>>>>
>>>>> So when we first start the program, i.e. the user hasn't entered any
>>>>> input yet, and #peek is called:
>>>>>
>>>>> 1. #atEnd returns false because Ctrl-D (or similar) hasn't been
>>>>> entered (assuming it is non-blocking).
>>>>> 2. peekBuffer is nil because we haven't previously called #peek.
>>>>> 3. The system now blocks on "self next".
>>>>>
>>>>>
>>>>> Just a reminder: for terminal input the end-of-file isn't reached
>>>>> until the user explicitly enters the end of file key (Ctrl-D).
>>>>>
>>>>> So, if there is no buffered input (either none has been entered yet,
>>>>> or all input has been consumed)
>>>>>
>>>>> #atEnd (after the patch) calls #primAtEnd:.
>>>>>
>>>>> At the moment, #primAtEnd: ends up calling the libc function feof(),
>>>>> which is non-blocking and answers the end-of-file flag for the FILE*.
>>>>> Since the user hasn't entered Ctrl-D, that's false.
>>>>>
>>>>> If we want to control iteration over the stream and ensure that we
>>>>> don't need to do a "stream next == nil" check, then #primAtEnd: is
>>>>> going to have to peek for the next character, and that means waiting
>>>>> for the user to enter that character.
>>>>>
>>>>> In c that is typically done using:
>>>>>
>>>>> atEnd = ungetc(fgetc(fp), fp);
>>>>>
>>>>> and fgetc() will block until the user enters something.
>>>>>
>>>>>> I have run your example testAtEnd.st now, and it works/fails as advertised.
>>>>>
>>>>> :-)
>>>>>
>>>>>
>>>>> Cheers,
>>>>> Alistair
>
>

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Re: Changed #atEnd primitive - #atEnd vs #next returning nil

Stephane Ducasse-3
In reply to this post by Sven Van Caekenberghe-2
I did not know about the NeoConsole. Nice because I wanted to build a
little REPL for my minilanguage implementation.

Stef

On Wed, Apr 11, 2018 at 8:47 PM, Sven Van Caekenberghe <[hidden email]> wrote:

> Alistair,
>
>> On 11 Apr 2018, at 19:42, Sven Van Caekenberghe <[hidden email]> wrote:
>>
>> I will send you some code later on.
>
> Today I arranged for my NeoConsole code (that normally works over a network connection) to work over stdio. Although I am not yet happy with every aspect of the implementation, it does work (using unaltered Zn streams and code). The foll
>
> $ cat /etc/issue
> Ubuntu 16.04.4 LTS
> $ mkdir pharo7
> $ cd pharo7/
> $ curl get.pharo.org/70+vm | bash
>   % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
>                                  Dload  Upload   Total   Spent    Left  Speed
> 100  3036  100  3036    0     0  36799      0 --:--:-- --:--:-- --:--:-- 37024
> Downloading the latest 70 Image:
>     http://files.pharo.org/get-files/70/pharo.zip
> Pharo.image
> Downloading the latest pharoVM:
>         http://files.pharo.org/get-files/70/pharo-linux-stable.zip
> pharo-vm/pharo
> Creating starter scripts pharo and pharo-ui
> On a 64-bit system? You must enable and install the 32-bit libraries
>    Please see http://pharo.org/gnu-linux-installation for detailed instructions
> $ ./pharo Pharo.image config http://mc.stfx.eu/Neo ConfigurationOfNeoConsole --install=bleedingEdge
> 'Installing ConfigurationOfNeoConsole bleedingEdge'
>
> Loading 1-baseline of ConfigurationOfNeoConsole...
> Fetched -> Neo-Console-Core-SvenVanCaekenberghe.24 --- http://mc.stfx.eu/Neo --- http://mc.stfx.eu/Neo
> Loaded -> Neo-Console-Core-SvenVanCaekenberghe.24 --- http://mc.stfx.eu/Neo --- cache
> ...finished 1-baseline
> $ ./pharo Pharo.image eval NeoConsoleStdio run
> Neo Console Pharo-7.0+alpha.build.760.sha.d2734dcabda799803c307365bcd120f92211d34a (32 Bit)
> pharo> 1+2
>
> 3
> pharo> 42 factorial
>
> 1405006117752879898543142606244511569936384000000000
> pharo> Stdio stdin
>
> StdioStream: #stdin
> pharo> ==
> self: StdioStream: #stdin
> class: StdioStream
> file: a File
> handle: #[148 213 25 107 160 197 105 247 0 0 0 0 0 0 0 0 0 1 255 1]
> forWrite: false
> peekBuffer: nil
> pharo> show StdioStream>>#atEnd
> StdioStream>>#atEnd
> atEnd
>
>         ^ file atEnd
> pharo> get process.list
> Morphic UI Process
> Delay Scheduling Process
> Low Space Watcher
> Input Event Fetcher Process
> Idle Process
> WeakArray Finalization Process
> CommandLine handler process
> pharo> quit
> Bye!
> a NeoConsoleStdio
>
> I know there are many approaches to a REPL, I don't claim mine is best, it is just the one that I have been using for years.
>
> In the above, I do not depend on EOF - just to be clear. The point being that there is no immediate fundamental problem.
>
> But there is something wrong with what is returned by Stdio stdin
>
> Sven
>
>
>

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Re: Changed #atEnd primitive - #atEnd vs #next returning nil

Sven Van Caekenberghe-2


> On 11 Apr 2018, at 21:44, Stephane Ducasse <[hidden email]> wrote:
>
> I did not know about the NeoConsole. Nice because I wanted to build a
> little REPL for my minilanguage implementation.

You are of course welcome to look at it.
But it is Pharo specific.
I use it to be able to hook/look into running headless server images.
For this it is super handy.

> Stef
>
> On Wed, Apr 11, 2018 at 8:47 PM, Sven Van Caekenberghe <[hidden email]> wrote:
>> Alistair,
>>
>>> On 11 Apr 2018, at 19:42, Sven Van Caekenberghe <[hidden email]> wrote:
>>>
>>> I will send you some code later on.
>>
>> Today I arranged for my NeoConsole code (that normally works over a network connection) to work over stdio. Although I am not yet happy with every aspect of the implementation, it does work (using unaltered Zn streams and code). The foll
>>
>> $ cat /etc/issue
>> Ubuntu 16.04.4 LTS
>> $ mkdir pharo7
>> $ cd pharo7/
>> $ curl get.pharo.org/70+vm | bash
>>  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
>>                                 Dload  Upload   Total   Spent    Left  Speed
>> 100  3036  100  3036    0     0  36799      0 --:--:-- --:--:-- --:--:-- 37024
>> Downloading the latest 70 Image:
>>    http://files.pharo.org/get-files/70/pharo.zip
>> Pharo.image
>> Downloading the latest pharoVM:
>>        http://files.pharo.org/get-files/70/pharo-linux-stable.zip
>> pharo-vm/pharo
>> Creating starter scripts pharo and pharo-ui
>> On a 64-bit system? You must enable and install the 32-bit libraries
>>   Please see http://pharo.org/gnu-linux-installation for detailed instructions
>> $ ./pharo Pharo.image config http://mc.stfx.eu/Neo ConfigurationOfNeoConsole --install=bleedingEdge
>> 'Installing ConfigurationOfNeoConsole bleedingEdge'
>>
>> Loading 1-baseline of ConfigurationOfNeoConsole...
>> Fetched -> Neo-Console-Core-SvenVanCaekenberghe.24 --- http://mc.stfx.eu/Neo --- http://mc.stfx.eu/Neo
>> Loaded -> Neo-Console-Core-SvenVanCaekenberghe.24 --- http://mc.stfx.eu/Neo --- cache
>> ...finished 1-baseline
>> $ ./pharo Pharo.image eval NeoConsoleStdio run
>> Neo Console Pharo-7.0+alpha.build.760.sha.d2734dcabda799803c307365bcd120f92211d34a (32 Bit)
>> pharo> 1+2
>>
>> 3
>> pharo> 42 factorial
>>
>> 1405006117752879898543142606244511569936384000000000
>> pharo> Stdio stdin
>>
>> StdioStream: #stdin
>> pharo> ==
>> self: StdioStream: #stdin
>> class: StdioStream
>> file: a File
>> handle: #[148 213 25 107 160 197 105 247 0 0 0 0 0 0 0 0 0 1 255 1]
>> forWrite: false
>> peekBuffer: nil
>> pharo> show StdioStream>>#atEnd
>> StdioStream>>#atEnd
>> atEnd
>>
>>        ^ file atEnd
>> pharo> get process.list
>> Morphic UI Process
>> Delay Scheduling Process
>> Low Space Watcher
>> Input Event Fetcher Process
>> Idle Process
>> WeakArray Finalization Process
>> CommandLine handler process
>> pharo> quit
>> Bye!
>> a NeoConsoleStdio
>>
>> I know there are many approaches to a REPL, I don't claim mine is best, it is just the one that I have been using for years.
>>
>> In the above, I do not depend on EOF - just to be clear. The point being that there is no immediate fundamental problem.
>>
>> But there is something wrong with what is returned by Stdio stdin
>>
>> Sven
>>
>>
>>
>


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Re: Changed #atEnd primitive - #atEnd vs #next returning nil

Eliot Miranda-2
Hi Sven,

On Wed, Apr 11, 2018 at 1:25 PM, Sven Van Caekenberghe <[hidden email]> wrote:


> On 11 Apr 2018, at 21:44, Stephane Ducasse <[hidden email]> wrote:
>
> I did not know about the NeoConsole. Nice because I wanted to build a
> little REPL for my minilanguage implementation.

You are of course welcome to look at it.
But it is Pharo specific.
I use it to be able to hook/look into running headless server images.
For this it is super handy.

Cool usage!  Could you tell me whether you type Smalltalk expressions into this to examine your running server?  The answer will be used in a related discussion on a mailing list not too distant from this one ;-)
 

> Stef
>
> On Wed, Apr 11, 2018 at 8:47 PM, Sven Van Caekenberghe <[hidden email]> wrote:
>> Alistair,
>>
>>> On 11 Apr 2018, at 19:42, Sven Van Caekenberghe <[hidden email]> wrote:
>>>
>>> I will send you some code later on.
>>
>> Today I arranged for my NeoConsole code (that normally works over a network connection) to work over stdio. Although I am not yet happy with every aspect of the implementation, it does work (using unaltered Zn streams and code). The foll
>>
>> $ cat /etc/issue
>> Ubuntu 16.04.4 LTS
>> $ mkdir pharo7
>> $ cd pharo7/
>> $ curl get.pharo.org/70+vm | bash
>>  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
>>                                 Dload  Upload   Total   Spent    Left  Speed
>> 100  3036  100  3036    0     0  36799      0 --:--:-- --:--:-- --:--:-- 37024
>> Downloading the latest 70 Image:
>>    http://files.pharo.org/get-files/70/pharo.zip
>> Pharo.image
>> Downloading the latest pharoVM:
>>        http://files.pharo.org/get-files/70/pharo-linux-stable.zip
>> pharo-vm/pharo
>> Creating starter scripts pharo and pharo-ui
>> On a 64-bit system? You must enable and install the 32-bit libraries
>>   Please see http://pharo.org/gnu-linux-installation for detailed instructions
>> $ ./pharo Pharo.image config http://mc.stfx.eu/Neo ConfigurationOfNeoConsole --install=bleedingEdge
>> 'Installing ConfigurationOfNeoConsole bleedingEdge'
>>
>> Loading 1-baseline of ConfigurationOfNeoConsole...
>> Fetched -> Neo-Console-Core-SvenVanCaekenberghe.24 --- http://mc.stfx.eu/Neo --- http://mc.stfx.eu/Neo
>> Loaded -> Neo-Console-Core-SvenVanCaekenberghe.24 --- http://mc.stfx.eu/Neo --- cache
>> ...finished 1-baseline
>> $ ./pharo Pharo.image eval NeoConsoleStdio run
>> Neo Console Pharo-7.0+alpha.build.760.sha.d2734dcabda799803c307365bcd120f92211d34a (32 Bit)
>> pharo> 1+2
>>
>> 3
>> pharo> 42 factorial
>>
>> 1405006117752879898543142606244511569936384000000000
>> pharo> Stdio stdin
>>
>> StdioStream: #stdin
>> pharo> ==
>> self: StdioStream: #stdin
>> class: StdioStream
>> file: a File
>> handle: #[148 213 25 107 160 197 105 247 0 0 0 0 0 0 0 0 0 1 255 1]
>> forWrite: false
>> peekBuffer: nil
>> pharo> show StdioStream>>#atEnd
>> StdioStream>>#atEnd
>> atEnd
>>
>>        ^ file atEnd
>> pharo> get process.list
>> Morphic UI Process
>> Delay Scheduling Process
>> Low Space Watcher
>> Input Event Fetcher Process
>> Idle Process
>> WeakArray Finalization Process
>> CommandLine handler process
>> pharo> quit
>> Bye!
>> a NeoConsoleStdio
>>
>> I know there are many approaches to a REPL, I don't claim mine is best, it is just the one that I have been using for years.
>>
>> In the above, I do not depend on EOF - just to be clear. The point being that there is no immediate fundamental problem.
>>
>> But there is something wrong with what is returned by Stdio stdin
>>
>> Sven
>>
>>
>>
>





--
_,,,^..^,,,_
best, Eliot
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Re: Changed #atEnd primitive - #atEnd vs #next returning nil

Ben Coman
In reply to this post by Sven Van Caekenberghe-2


On 12 April 2018 at 04:25, Sven Van Caekenberghe <[hidden email]> wrote:


> On 11 Apr 2018, at 21:44, Stephane Ducasse <[hidden email]> wrote:
>
> I did not know about the NeoConsole. Nice because I wanted to build a
> little REPL for my minilanguage implementation.

You are of course welcome to look at it.
But it is Pharo specific.
I use it to be able to hook/look into running headless server images.
For this it is super handy.

A description of how to set that up would make a nice blog post.
cheers -ben 
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Re: Changed #atEnd primitive - #atEnd vs #next returning nil

alistairgrant
In reply to this post by Nicolas Cellier
On 11 April 2018 at 19:42, Nicolas Cellier
<[hidden email]> wrote:

>
>
> 2018-04-11 19:08 GMT+02:00 Alistair Grant <[hidden email]>:
>>
>> Hi Sven,
>>
>> On 11 April 2018 at 18:53, Sven Van Caekenberghe <[hidden email]> wrote:
>> > Something is off (and/or I am getting crazy, probably both).
>> >
>> > $ ./pharo --headless Pharo.image eval '(FileStream stdin binary; next:
>> > 3)'
>> > 123
>> > #[49]
>> >
>> > ??
>> >
>> > This should return #[49 50 51] AFAIK.
>>
>> I haven't checked properly, but I can take a guess at this...
>>
>> The file read primitive in FilePlugin tries to read from stdin 1
>> character at a time (presumably to get around the line buffering that
>> is done, but I haven't gone through the history.  At one time I think
>> it modified the terminal settings, but that code is #if'd out).  For
>> all other streams it attempts to read the requested number of
>> characters.
>>
>> StandardFileStream>>readInto:startingAt:count: assumes that
>> primitiveFileRead will always attempt to read count bytes, but it
>> actually only attempts to read 1.
>>
>> Cheers,
>> Alistair
>>
>
> https://github.com/OpenSmalltalk/opensmalltalk-vm/issues/150

Thanks!  I'd already looked at this routine and found it strangely
constructed.  Having some background discussion will help a lot.

Cheers,
Alistair

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Re: Changed #atEnd primitive - #atEnd vs #next returning nil

K K Subbu
In reply to this post by alistairgrant
On Wednesday 11 April 2018 10:38 PM, Alistair Grant wrote:
> StandardFileStream>>readInto:startingAt:count: assumes that
> primitiveFileRead will always attempt to read count bytes, but it
> actually only attempts to read 1.

StandardFileStream>>#basicNext uses

   position < readLimit ifFalse:

and does not check if the primRead returns < 0. Instead it should call
whileFalse: and check if primRead returns <= 0 to check for EOF or error.

#primRead:... returns an error if the primitive fails and the file is
closed. It should instead check for EOF or error and then return -1,
otherwise it should return 0 (Data not ready?). Raise an error only if
the underlying primitive fails for non-EOF cases.

Regards .. Subbu

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Re: Changed #atEnd primitive - #atEnd vs #next returning nil

alistairgrant
In reply to this post by Sven Van Caekenberghe-2
Hi Sven,

On 11 April 2018 at 20:47, Sven Van Caekenberghe <[hidden email]> wrote:

> Alistair,
>
>> On 11 Apr 2018, at 19:42, Sven Van Caekenberghe <[hidden email]> wrote:
>>
>> I will send you some code later on.
>
> Today I arranged for my NeoConsole code (that normally works over a network connection) to work over stdio. Although I am not yet happy with every aspect of the implementation, it does work (using unaltered Zn streams and code). The foll
>
> $ cat /etc/issue
> Ubuntu 16.04.4 LTS
> $ mkdir pharo7
> $ cd pharo7/
> $ curl get.pharo.org/70+vm | bash
>   % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
>                                  Dload  Upload   Total   Spent    Left  Speed
> 100  3036  100  3036    0     0  36799      0 --:--:-- --:--:-- --:--:-- 37024
> Downloading the latest 70 Image:
>     http://files.pharo.org/get-files/70/pharo.zip
> Pharo.image
> Downloading the latest pharoVM:
>         http://files.pharo.org/get-files/70/pharo-linux-stable.zip
> pharo-vm/pharo
> Creating starter scripts pharo and pharo-ui
> On a 64-bit system? You must enable and install the 32-bit libraries
>    Please see http://pharo.org/gnu-linux-installation for detailed instructions
> $ ./pharo Pharo.image config http://mc.stfx.eu/Neo ConfigurationOfNeoConsole --install=bleedingEdge
> 'Installing ConfigurationOfNeoConsole bleedingEdge'
>
> Loading 1-baseline of ConfigurationOfNeoConsole...
> Fetched -> Neo-Console-Core-SvenVanCaekenberghe.24 --- http://mc.stfx.eu/Neo --- http://mc.stfx.eu/Neo
> Loaded -> Neo-Console-Core-SvenVanCaekenberghe.24 --- http://mc.stfx.eu/Neo --- cache
> ...finished 1-baseline
> $ ./pharo Pharo.image eval NeoConsoleStdio run
> Neo Console Pharo-7.0+alpha.build.760.sha.d2734dcabda799803c307365bcd120f92211d34a (32 Bit)
> pharo> 1+2
>
> 3
> pharo> 42 factorial
>
> 1405006117752879898543142606244511569936384000000000
> pharo> Stdio stdin
>
> StdioStream: #stdin
> pharo> ==
> self: StdioStream: #stdin
> class: StdioStream
> file: a File
> handle: #[148 213 25 107 160 197 105 247 0 0 0 0 0 0 0 0 0 1 255 1]
> forWrite: false
> peekBuffer: nil
> pharo> show StdioStream>>#atEnd
> StdioStream>>#atEnd
> atEnd
>
>         ^ file atEnd
> pharo> get process.list
> Morphic UI Process
> Delay Scheduling Process
> Low Space Watcher
> Input Event Fetcher Process
> Idle Process
> WeakArray Finalization Process
> CommandLine handler process
> pharo> quit
> Bye!
> a NeoConsoleStdio
>
> I know there are many approaches to a REPL, I don't claim mine is best, it is just the one that I have been using for years.
>
> In the above, I do not depend on EOF - just to be clear. The point being that there is no immediate fundamental problem.


Cool.  I've wanted to try NeoConsole for a while (I've got a Raspberry
Pi monitoring temperatures and wanted to use it to work on the Pi) but
hadn't made the time.

But... :-)


$ vm/pharo Pharo7.0-64bit-d2734dc.image eval NeoConsoleStdio run
Neo Console Pharo-7.0+alpha.build.760.sha.d2734dcabda799803c307365bcd120f92211d34a
(64 Bit)
pharo> 4+3

7
pharo> [Ctrl-D]
MessageNotUnderstood: receiver of "<" is nil
UndefinedObject(Object)>>doesNotUnderstand: #<
ZnUTF8Encoder>>nextCodePointFromStream:
ZnUTF8Encoder(ZnCharacterEncoder)>>nextFromStream:
ZnCharacterReadStream>>nextElement
ZnCharacterReadStream(ZnEncodedReadStream)>>next
[ :out |
| eol char |
eol := false.
[ eol ]
whileFalse: [ char := readStream next.
(char isNil or: [ char == lf ])
ifTrue: [ eol := true ]
ifFalse: [ char == cr
ifTrue: [ eol := true.
readStream peekFor: lf ]
ifFalse: [ out nextPut: char ] ] ] ] in ZnFastLineReader>>nextLine in
Block: [ :out | ...
ZnFastLineReader>>streamContents:
ZnFastLineReader>>nextLine
[ lineReader nextLine trimBoth ] in NeoConsoleStdio>>readInputFrom: in
Block: [ lineReader nextLine trimBoth ]
BlockClosure>>on:do:
NeoConsoleStdio>>readInputFrom:
NeoConsoleStdio>>executeRequestResponseLoop
NeoConsoleStdio>>run
NeoConsoleStdio class>>run
UndefinedObject>>DoIt


In your example you've carefully exited by some other means than
signalling end-of-file (Ctrl-D).

I don't think we can reasonably say "if you write code with Zinc
streams, ensure that none of your users ever press Ctrl-D, they must
always type 'quit' (or whatever)".



>
> But there is something wrong with what is returned by Stdio stdin

Right, that's the bug I was addressing stdio.cs.  I've got a note to
open an issue and submit a PR.

Cheers,
Alistair

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Re: Changed #atEnd primitive - #atEnd vs #next returning nil

Sven Van Caekenberghe-2


> On 12 Apr 2018, at 08:33, Alistair Grant <[hidden email]> wrote:
>
> Hi Sven,
>
> On 11 April 2018 at 20:47, Sven Van Caekenberghe <[hidden email]> wrote:
>> Alistair,
>>
>>> On 11 Apr 2018, at 19:42, Sven Van Caekenberghe <[hidden email]> wrote:
>>>
>>> I will send you some code later on.
>>
>> Today I arranged for my NeoConsole code (that normally works over a network connection) to work over stdio. Although I am not yet happy with every aspect of the implementation, it does work (using unaltered Zn streams and code). The foll
>>
>> $ cat /etc/issue
>> Ubuntu 16.04.4 LTS
>> $ mkdir pharo7
>> $ cd pharo7/
>> $ curl get.pharo.org/70+vm | bash
>>  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
>>                                 Dload  Upload   Total   Spent    Left  Speed
>> 100  3036  100  3036    0     0  36799      0 --:--:-- --:--:-- --:--:-- 37024
>> Downloading the latest 70 Image:
>>    http://files.pharo.org/get-files/70/pharo.zip
>> Pharo.image
>> Downloading the latest pharoVM:
>>        http://files.pharo.org/get-files/70/pharo-linux-stable.zip
>> pharo-vm/pharo
>> Creating starter scripts pharo and pharo-ui
>> On a 64-bit system? You must enable and install the 32-bit libraries
>>   Please see http://pharo.org/gnu-linux-installation for detailed instructions
>> $ ./pharo Pharo.image config http://mc.stfx.eu/Neo ConfigurationOfNeoConsole --install=bleedingEdge
>> 'Installing ConfigurationOfNeoConsole bleedingEdge'
>>
>> Loading 1-baseline of ConfigurationOfNeoConsole...
>> Fetched -> Neo-Console-Core-SvenVanCaekenberghe.24 --- http://mc.stfx.eu/Neo --- http://mc.stfx.eu/Neo
>> Loaded -> Neo-Console-Core-SvenVanCaekenberghe.24 --- http://mc.stfx.eu/Neo --- cache
>> ...finished 1-baseline
>> $ ./pharo Pharo.image eval NeoConsoleStdio run
>> Neo Console Pharo-7.0+alpha.build.760.sha.d2734dcabda799803c307365bcd120f92211d34a (32 Bit)
>> pharo> 1+2
>>
>> 3
>> pharo> 42 factorial
>>
>> 1405006117752879898543142606244511569936384000000000
>> pharo> Stdio stdin
>>
>> StdioStream: #stdin
>> pharo> ==
>> self: StdioStream: #stdin
>> class: StdioStream
>> file: a File
>> handle: #[148 213 25 107 160 197 105 247 0 0 0 0 0 0 0 0 0 1 255 1]
>> forWrite: false
>> peekBuffer: nil
>> pharo> show StdioStream>>#atEnd
>> StdioStream>>#atEnd
>> atEnd
>>
>>        ^ file atEnd
>> pharo> get process.list
>> Morphic UI Process
>> Delay Scheduling Process
>> Low Space Watcher
>> Input Event Fetcher Process
>> Idle Process
>> WeakArray Finalization Process
>> CommandLine handler process
>> pharo> quit
>> Bye!
>> a NeoConsoleStdio
>>
>> I know there are many approaches to a REPL, I don't claim mine is best, it is just the one that I have been using for years.
>>
>> In the above, I do not depend on EOF - just to be clear. The point being that there is no immediate fundamental problem.
>
>
> Cool.  I've wanted to try NeoConsole for a while (I've got a Raspberry
> Pi monitoring temperatures and wanted to use it to work on the Pi) but
> hadn't made the time.
>
> But... :-)
>
>
> $ vm/pharo Pharo7.0-64bit-d2734dc.image eval NeoConsoleStdio run
> Neo Console Pharo-7.0+alpha.build.760.sha.d2734dcabda799803c307365bcd120f92211d34a
> (64 Bit)
> pharo> 4+3
>
> 7
> pharo> [Ctrl-D]
> MessageNotUnderstood: receiver of "<" is nil
> UndefinedObject(Object)>>doesNotUnderstand: #<
> ZnUTF8Encoder>>nextCodePointFromStream:
> ZnUTF8Encoder(ZnCharacterEncoder)>>nextFromStream:
> ZnCharacterReadStream>>nextElement
> ZnCharacterReadStream(ZnEncodedReadStream)>>next
> [ :out |
> | eol char |
> eol := false.
> [ eol ]
> whileFalse: [ char := readStream next.
> (char isNil or: [ char == lf ])
> ifTrue: [ eol := true ]
> ifFalse: [ char == cr
> ifTrue: [ eol := true.
> readStream peekFor: lf ]
> ifFalse: [ out nextPut: char ] ] ] ] in ZnFastLineReader>>nextLine in
> Block: [ :out | ...
> ZnFastLineReader>>streamContents:
> ZnFastLineReader>>nextLine
> [ lineReader nextLine trimBoth ] in NeoConsoleStdio>>readInputFrom: in
> Block: [ lineReader nextLine trimBoth ]
> BlockClosure>>on:do:
> NeoConsoleStdio>>readInputFrom:
> NeoConsoleStdio>>executeRequestResponseLoop
> NeoConsoleStdio>>run
> NeoConsoleStdio class>>run
> UndefinedObject>>DoIt
>
>
> In your example you've carefully exited by some other means than
> signalling end-of-file (Ctrl-D).
>
> I don't think we can reasonably say "if you write code with Zinc
> streams, ensure that none of your users ever press Ctrl-D, they must
> always type 'quit' (or whatever)".

I left that open as an exercise for the reader - I knew you would try that ;-)

The code was originally written for network streams and there it catches ConnectionClosed which is the network stream equivalent of EOF (more or less).

I think we need something like an EndOfStream exception which should be thrown in that case, instead of returning nil.

Returning nil from ZnCharacterReadStream or ZnCharacterEncoder when the stream is EOF is wrong IMHO. The stream being EOF is an exceptional situation (even though it is relatively common) and there is always #atEnd that works well in 99% of the cases.

AFAIK that is also the design decision taking by Xtreams (where I believe the Incomplete exception replaces #atEnd).

>> But there is something wrong with what is returned by Stdio stdin
>
> Right, that's the bug I was addressing stdio.cs.  I've got a note to
> open an issue and submit a PR.
>
> Cheers,
> Alistair


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Re: Changed #atEnd primitive - #atEnd vs #next returning nil

Sven Van Caekenberghe-2
In reply to this post by Ben Coman


> On 12 Apr 2018, at 04:07, Ben Coman <[hidden email]> wrote:
>
>
>
> On 12 April 2018 at 04:25, Sven Van Caekenberghe <[hidden email]> wrote:
>
>
> > On 11 Apr 2018, at 21:44, Stephane Ducasse <[hidden email]> wrote:
> >
> > I did not know about the NeoConsole. Nice because I wanted to build a
> > little REPL for my minilanguage implementation.
>
> You are of course welcome to look at it.
> But it is Pharo specific.
> I use it to be able to hook/look into running headless server images.
> For this it is super handy.
>
> A description of how to set that up would make a nice blog post.

It is part of, and partially documented in https://github.com/svenvc/pharo-server-tools

But maybe I'll write something about it, yes.

> cheers -ben


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Re: Changed #atEnd primitive - #atEnd vs #next returning nil

Sven Van Caekenberghe-2
In reply to this post by Eliot Miranda-2


> On 12 Apr 2018, at 03:15, Eliot Miranda <[hidden email]> wrote:
>
> Hi Sven,
>
> On Wed, Apr 11, 2018 at 1:25 PM, Sven Van Caekenberghe <[hidden email]> wrote:
>
>
> > On 11 Apr 2018, at 21:44, Stephane Ducasse <[hidden email]> wrote:
> >
> > I did not know about the NeoConsole. Nice because I wanted to build a
> > little REPL for my minilanguage implementation.
>
> You are of course welcome to look at it.
> But it is Pharo specific.
> I use it to be able to hook/look into running headless server images.
> For this it is super handy.
>
> Cool usage!  Could you tell me whether you type Smalltalk expressions into this to examine your running server?  The answer will be used in a related discussion on a mailing list not too distant from this one ;-)

Yes of course, that it the whole purpose, to type in expressions and to manipulate objects in a running image. I recently added options to look at code and change/add methods. All very primitive, but when in trouble, it works well.

> > Stef
> >
> > On Wed, Apr 11, 2018 at 8:47 PM, Sven Van Caekenberghe <[hidden email]> wrote:
> >> Alistair,
> >>
> >>> On 11 Apr 2018, at 19:42, Sven Van Caekenberghe <[hidden email]> wrote:
> >>>
> >>> I will send you some code later on.
> >>
> >> Today I arranged for my NeoConsole code (that normally works over a network connection) to work over stdio. Although I am not yet happy with every aspect of the implementation, it does work (using unaltered Zn streams and code). The foll
> >>
> >> $ cat /etc/issue
> >> Ubuntu 16.04.4 LTS
> >> $ mkdir pharo7
> >> $ cd pharo7/
> >> $ curl get.pharo.org/70+vm | bash
> >>  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
> >>                                 Dload  Upload   Total   Spent    Left  Speed
> >> 100  3036  100  3036    0     0  36799      0 --:--:-- --:--:-- --:--:-- 37024
> >> Downloading the latest 70 Image:
> >>    http://files.pharo.org/get-files/70/pharo.zip
> >> Pharo.image
> >> Downloading the latest pharoVM:
> >>        http://files.pharo.org/get-files/70/pharo-linux-stable.zip
> >> pharo-vm/pharo
> >> Creating starter scripts pharo and pharo-ui
> >> On a 64-bit system? You must enable and install the 32-bit libraries
> >>   Please see http://pharo.org/gnu-linux-installation for detailed instructions
> >> $ ./pharo Pharo.image config http://mc.stfx.eu/Neo ConfigurationOfNeoConsole --install=bleedingEdge
> >> 'Installing ConfigurationOfNeoConsole bleedingEdge'
> >>
> >> Loading 1-baseline of ConfigurationOfNeoConsole...
> >> Fetched -> Neo-Console-Core-SvenVanCaekenberghe.24 --- http://mc.stfx.eu/Neo --- http://mc.stfx.eu/Neo
> >> Loaded -> Neo-Console-Core-SvenVanCaekenberghe.24 --- http://mc.stfx.eu/Neo --- cache
> >> ...finished 1-baseline
> >> $ ./pharo Pharo.image eval NeoConsoleStdio run
> >> Neo Console Pharo-7.0+alpha.build.760.sha.d2734dcabda799803c307365bcd120f92211d34a (32 Bit)
> >> pharo> 1+2
> >>
> >> 3
> >> pharo> 42 factorial
> >>
> >> 1405006117752879898543142606244511569936384000000000
> >> pharo> Stdio stdin
> >>
> >> StdioStream: #stdin
> >> pharo> ==
> >> self: StdioStream: #stdin
> >> class: StdioStream
> >> file: a File
> >> handle: #[148 213 25 107 160 197 105 247 0 0 0 0 0 0 0 0 0 1 255 1]
> >> forWrite: false
> >> peekBuffer: nil
> >> pharo> show StdioStream>>#atEnd
> >> StdioStream>>#atEnd
> >> atEnd
> >>
> >>        ^ file atEnd
> >> pharo> get process.list
> >> Morphic UI Process
> >> Delay Scheduling Process
> >> Low Space Watcher
> >> Input Event Fetcher Process
> >> Idle Process
> >> WeakArray Finalization Process
> >> CommandLine handler process
> >> pharo> quit
> >> Bye!
> >> a NeoConsoleStdio
> >>
> >> I know there are many approaches to a REPL, I don't claim mine is best, it is just the one that I have been using for years.
> >>
> >> In the above, I do not depend on EOF - just to be clear. The point being that there is no immediate fundamental problem.
> >>
> >> But there is something wrong with what is returned by Stdio stdin
> >>
> >> Sven
> >>
> >>
> >>
> >
>
>
>
>
>
> --
> _,,,^..^,,,_
> best, Eliot


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Re: Changed #atEnd primitive - #atEnd vs #next returning nil

alistairgrant
In reply to this post by Sven Van Caekenberghe-2
Hi Sven,

On Thu, Apr 12, 2018 at 09:23:21AM +0200, Sven Van Caekenberghe wrote:

>
>
> > On 12 Apr 2018, at 08:33, Alistair Grant <[hidden email]> wrote:
> >
> > ...
> >
> > In your example you've carefully exited by some other means than
> > signalling end-of-file (Ctrl-D).
> >
> > I don't think we can reasonably say "if you write code with Zinc
> > streams, ensure that none of your users ever press Ctrl-D, they must
> > always type 'quit' (or whatever)".
>
> I left that open as an exercise for the reader - I knew you would try that ;-)

Glad that I didn't disappoint. :-)


> The code was originally written for network streams and there it
> catches ConnectionClosed which is the network stream equivalent of EOF
> (more or less).
>
> I think we need something like an EndOfStream exception which should
> be thrown in that case, instead of returning nil.
>
> Returning nil from ZnCharacterReadStream or ZnCharacterEncoder when
> the stream is EOF is wrong IMHO. The stream being EOF is an
> exceptional situation (even though it is relatively common) and there
> is always #atEnd that works well in 99% of the cases.
>
> AFAIK that is also the design decision taking by Xtreams (where I
> believe the Incomplete exception replaces #atEnd).

OK, this brings us full-circle.

Earlier in the thread we wrote:


On Tue, Apr 10, 2018 at 11:54:39PM +0200, Sven Van Caekenberghe wrote:

> Alistair,
>
> I am replying in-between, please don't take my remarks as being
> negative, I just like to straighten things out as clear as possible.
>
> > On 10 Apr 2018, at 22:14, Alistair Grant <[hidden email]> wrote:
> >
> > At this point I think there are three options:
> >
> > 1. Modify Zinc to check the return value of #next instead of using #atEnd.
> >
> > This is what all existing character / byte oriented streams in Squeak
> > and Pharo do.  At that point the Zinc streams can be used on all file
> > / stdio input and output.
>
> I agree that such code exists in many places, but there is lots of
> stream reading that does not check for nils.
>
> > 2. Modify all streams to signal EOF in some other way, i.e. a sentinel
> > or notification / exception.
> >
> > This is what we were discussing below.  But it is a decent chunk of
> > work with significant impact on the existing code base.
>
> Agreed. This would be a future extension.


I agree that raising an exception is a nicer solution (although for
anyone who disagrees I'll also admit that there is a subjective element to
that assessment).

But the existing behaviour of returning nil on EOF has been around for a
long time and works reasonably well, and as we agreed here, changing that
behaviour will have a significant impact on the existing code base.

None of this excludes Zinc streams adopting exceptions at any time in
the future.

So I'm going to respectfully disagree and say that I think to raise a
MNU instead of returning nil is wrong, and that changing the Zinc
streams isn't such a big deal.

Cheers,
Alistair

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Re: Changed #atEnd primitive - #atEnd vs #next returning nil

alistairgrant
On 12 April 2018 at 10:48, Alistair Grant <[hidden email]> wrote:
>
> So I'm going to respectfully disagree and say that I think to raise a
> MNU instead of returning nil is wrong, and that changing the Zinc
> streams isn't such a big deal.

Sorry Sven, this sounds like I'm suggesting that your planning to
leave the MNU in there, which would be rather rude of me, but isn't
what I meant at all.

But I do think Zinc streams should handle #next returning nil before
#atEnd answers true.

Cheers,
Alistair

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Re: Changed #atEnd primitive - #atEnd vs #next returning nil

alistairgrant
In reply to this post by Sven Van Caekenberghe-2
On 11 April 2018 at 20:47, Sven Van Caekenberghe <[hidden email]> wrote:
>
> But there is something wrong with what is returned by Stdio stdin
>

I've opened https://pharo.fogbugz.com/f/cases/21692/StdioStream-incorrectly-delegates-atEnd-and-position-to-file

PR in progress.

Cheers,
Alistair

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Re: Changed #atEnd primitive - #atEnd vs #next returning nil

Stephane Ducasse-3
Thanks!!!!

On Thu, Apr 12, 2018 at 5:06 PM, Alistair Grant <[hidden email]> wrote:

> On 11 April 2018 at 20:47, Sven Van Caekenberghe <[hidden email]> wrote:
>>
>> But there is something wrong with what is returned by Stdio stdin
>>
>
> I've opened https://pharo.fogbugz.com/f/cases/21692/StdioStream-incorrectly-delegates-atEnd-and-position-to-file
>
> PR in progress.
>
> Cheers,
> Alistair
>

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