Hi. #next returning nil is definitely looks bad because we will always have case when nil value will not means the end:
#(1 nil 2) readSteam next; next; atEnd But I understand that in many cases analysing #next for nil is much more suitable than #atEnd. I am sure that it can be always avoided but it can be not easy to do. Alternatively we can reify real EndOfStream object which will be used as result of reading operation when stream is at end. It can provide nice API like #ifEndOfStream:. which will reflect intention in much cleaner way than ifNil: checks. 2018-04-04 12:00 GMT+02:00 Sven Van Caekenberghe <s...@stfx.eu>: > > > > On 4 Apr 2018, at 11:38, Nicolas Cellier <nicolas.cellier.aka.nice@ > gmail.com> wrote: > > > > Hi Sven, > > See also discussion at https://github.com/OpenSmalltalk/opensmalltalk- > vm/pull/232 > > Thanks Nicolas, I had already seen parts of it. > > Now, I still want image level changes to be based on clear semantic > definitions of the abstract stream API, we're not just talking about file > or unix streams, the general Smalltalk concept. > > For reading, they are IMHO, > > #next > #readInto:startingAt:count: > #peek > #atEnd > #upToEnd (can be derived but still the semantics are important in relation > to #atEnd) > > For writing, we have > > #nextPut: > #next:putAll:startingAt: > #flush > > For both, we have > > #atEnd > #close > #closed (new) > > So, I know, #next returning nil exists, but is it universally/officially > defined as such ? Where is that documented ? > > Positioning, sizing are not universal, IMHO, but should be clearly defined > as well. > > > 2018-04-04 11:32 GMT+02:00 Sven Van Caekenberghe <s...@stfx.eu>: > > Somehow, somewhere there was a change to the implementation of the > primitive called by some streams' #atEnd. > > > > IIRC, someone said it is implemented as 'remaining size being zero' and > some virtual unix files like /dev/random are zero sized. > > > > Now, all kinds of changes are being done image size to work around this. > > > > 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 ? > > > > 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 > > > > > > > > > > >
