How about #peekAhead? - HH
> -------- Original Message -------- > Subject: Re: [Pharo-users] Peeking at a stream > Local Time: November 2, 2017 9:28 AM > UTC Time: November 2, 2017 1:28 PM > From: aglyn...@gmail.com > To: Any question about pharo is welcome <pharo-users@lists.pharo.org> > > Perhaps #keepStateWhile or something similar might be better than > #unchangedDuring ? > > Sent from [Mail](https://go.microsoft.com/fwlink/?LinkId=550986) for Windows > 10 > > From: [Prof. Andrew P. Black](mailto:bl...@cs.pdx.edu) > Sent: Thursday, November 2, 2017 5:00 AM > To: [Any question about pharo is welcome](mailto:pharo-users@lists.pharo.org) > Subject: [Pharo-users] Peeking at a stream > > I sometimes find, when working with a stream, that I need to "peek ahead” a > few items, without disturbing the state of the stream. The message stream > peek gives me the next item, but doesn’t generalize to multiple items, So I > end up writing code like this: > > findSomething > > | savedPosition result | > > savedPosition := stream position. > stream position: start. > “code involving various manipulations of stream, including > stream next" > result := stream position + 1. > stream position: savedPosition. > > ^ result > > This code involves at least two temps, is not very easy to read, and risks > not resetting the stream properly if I do a return. > > It seems to me that a better solution would be what Kent Beck calls an > “execute around” method: > > findSomething > > ^ stream unchangedDuring: [ :s | > > “code involving various manipulations of stream, > including stream next" > > stream position + 1 ] > > I’m not sure that I like the name #unchangedDuring:; perhaps you can think of > a better one? > > The implementation of this would be > > PositionableStream >> #unchangedDuring: aBlock > > "execute aBlock with self as argument. Ensure that > when this method returns, > > I still have my current state." > > | savedPosition | > > savedPosition := self position. > ^ [ aBlock value: self ] ensure: [ self position: > savedPosition ] > > or perhaps > > PositionableStream >> #unchangedDuring: aBlock > "execute aBlock with self as argument. Ensure that > when this method returns, > > I still have my current state." > > ^ [ aBlock value: self copy ] > > which might be better in the case that the stream is a file stream and aBlock > causes the buffer to be refreshed from the disk. > > - Do other Smalltalks have a method like this? > - Does it already exist in Pharo, somewhere that I’ve failed to look? > - Would it be a worthwhile addition to Pharo? > - What would be a good name?
