Since 'abc' includesSubstring: ''. "true" 'abc' indexOfSubCollection: ''. "0"
and following basic principles, my first reaction would also be that 'abc' beginsWith: ''. 'abc' endsWith: ''. should both be true. On the other hand, this is really a degenerate case. You know the answer upfront (it does not depend on the actual receiver) and thus it does not tell you much. I vote for this to be a bug. > On 20 Apr 2022, at 14:07, Richard O'Keefe <rao...@gmail.com> wrote: > > I've just tracked down a nasty little problem > porting some code to Pharo. As a result, I > have added to the comments in my own versions > of these methods. beginsWith: aSequence > "Answer true if aSequence is a prefix of the receiver. > This makes sense for all sequences. > There is a compatibility issue concerning 'abc' beginsWith: '' > + VisualWorks, Dolphin, astc, GNU ST (where the method is > called #startsWith:) and VisualAge (where the method > is called #wbBeginsWith:) > agree than EVERY sequence begins with an empty prefix. > - Squeak and Pharo > agree that NO sequence begins with an empty sequence. > # ST/X chooses compatibility with Squeak, heaving a big unhappy > sigh, and adds #startsWith: to have something sensible to use. > Now ST/X *thinks* it is compatible with VW, though it isn't, so > I wonder if this was a bug that VW fixed and Squeak didn't? > astc goes with the majority here. This is also compatible with > Haskell, ML, and with StartsWith in C# and startsWith in Java." > ^self beginsWith: aSequence ignoringCase: false > > endsWith: aSequence > "Answer true if aSequence is a suffix of the receiver. > This makes sense for all sequences. > There is a compatibility issue concerning 'abc' endsWith: ''. > + VisualWorks, Dolphin, astc, GNU ST, and VisualAge (where > the method is called #wbEndsWith:) > agree that EVERY sequence ends with an empty suffix. > - Squeak and Pharo > agree that NO sequence ends with an empty suffix. > # ST/X chooses compatibility with the majority, apparently > unaware that this makes #beginsWith: and #endsWith: inconsistent. > astc goes with the majority here. This is also compatible with > Haskell, ML, C#, and Java." > ^self endsWith: aSequence ignoringCase: false > > Does anyone have any idea > - why Squeak and Pharo are the odd ones out? > - why anyone thought making #beginsWith: and #endsWith:, um, "quirky" > was a good idea (it's pretty standard in books on the theory of > strings to define "x is a prefix of y iff there is a z such that > y = x concatenated with z") > > I was about to try to file a bug report for the first time, > then realised that maybe other people don't think this IS a bug. > > >
