Hi Will, Thanks for taking the time to describe the changes between editions. I'll read through this in detail later.
Dan also contacted me off list and convinced me to buy it, as I said to him, I could probably also use more placemats to catch the baba ganoush stains! I honestly don't know why I hesitated. Many thanks, your work, and that of the minikanren community has been a joy to follow. R. On Monday, 10 September 2018 06:13:57 UTC+1, William Byrd wrote: > Hi Rick! > > > I've had a treasured copy of the reasoned schemer for many years, and > recently noticed that there's a second edition. > > Indeed there is, finally! ;) > > > Can anyone tell me what's new? And whether it's worth buying if you > have a first edition copy? > > > > Is the main difference that it's based on an implementation of > microkanren rather than minikanren? > > I'd say there are four big differences in the second edition. > > First, we simplified the miniKanren language in several critical ways. > The second edition only has one type of == (which always uses the > occur check), an improved conde that replaces the conde and condi from > the first edition, and an improved fresh that removes the need for > alli. I think this this is a huge improvement pedagogically, since > you needn't chose between the operator variants every time you write a > relation. And, from a design standpoint, I think it is far better to > have 3 core operators rather than 6. (I don't count condu or conda as > core operators--they are still in the book, though). > > Another simplification remove much the 'Schemely-ness' of the logic > language. Instead of (define appendo (lambda (l s out) ...)), we use > a new 'defrel' form that combines the jobs of 'define' and 'lambda'. > The purpose is to make the language more stand-alone--for example, if > you wanted to write an interpreter or compiler for the language of the > book, you could now do it without having to implement 'define', > 'lambda', or other Schemely constructs. I was hesitant about this > change for a while, but have come to appreciate it. 'defrel' is just > a Scheme macro, of course, so you aren't really losing any of the > power, but it does make the semantics a bit more clear, and avoids > some classic errors in using the language (such as forgetting to add a > '(fresh () ...)' inside any lambda that includes multiple goal > expressions). > > Second, we simplified the implementation, effectively splitting it > into a microKanren part, and a miniKanren part. The microKanren part > is explained in detail in Chapter 10, while the miniKanren part is > implemented using macros in Appendix A, after a brief explanation of > Scheme macros. We found that the Scheme macros in the first edition > confused most readers, and also made it harder to port miniKanren from > Scheme to another host language. By moving all the macros to an > appendix, and adding a brief explanation of macros, we hope to avoid > this confusion. > > Third, we tried to improve the explanation of concepts, based on the > feedback we've received over the past 13 years. We completely rewrote > Chapter 1 to allow it to build up the ideas in a (hopefully) more > logical fashion. We also added Translation rules, to make explicit > how to translate Scheme functions into miniKanren relations. I think > we usually succeeded in making the explanations more clear, but a few > of the older explanations may appeal to some readers. > > We also simplified the notation-- we replaced the bold parens and > italic variables with explicit quasiquotes and unquotes, for example, > and tried to make it more clear how to type in code from the book. > > Fourth, the book contains a new Preface, Forward, and Afterward, to > better give context to the work. > > > Whether it is worth reading the new edition probably depends on how > well you understand the first edition. If you have already > implemented microKanren, have used modern versions of miniKanren or > core.logic, have followed recent work on miniKanren, watched my > tutorials, etc., there probably won't be many surprises for you. > > If you struggled with the implementation or some of the explanations > in the first edition, or are not completely comfortable with the > miniKanren language, I think the new edition should help clarify those > concepts. > > In short, we rewrote and simplified much of the book, but the core > ideas are the same. As Dan likes to say, this is the edition we wish > we had written 13 years ago, but we didn't know enough then to write > it. > > I should also point out that the book does *not* include constraints > other than unification, interpreters, program synthesis, or other more > advanced miniKanren topics. We found it too difficult to include all > those ideas in a single book and keep it 'little'. (Believer me, we > tried! :)) Hopefully you will see more on those topics in the > future... > > I should also point out that the code for the new implementation is > available online: > > https://github.com/TheReasonedSchemer2ndEd/CodeFromTheReasonedSchemer2ndEd > > This implementation is similar in spirit to microKanren: > > http://webyrd.net/scheme-2013/papers/HemannMuKanren2013.pdf > > https://github.com/jasonhemann/microKanren > > > > Does microkanren have different semantics to minikanren? I'd initially > thought it was mainly just a smaller and simpler implementation, however > I've also seen comments indicating it changes the search strategy. Any > pointers to resources discussing the differences between the two would also > be greatly appreciated. > > The microKanren paper above discusses the search strategy--it is > similar in spirit to the old search, but can produce answers in a > different order. The exact search strategy used by miniKanren isn't > set in stone--we always use an interleaved, complete, biased search, > but the exact details differ among implementations. It is true that > the order of answers may change depending on these details, but > miniKanren's semantics make no guarantees about the order in which > answers are returned. > > > Hope this helps! > > --Will > > > > R. > > > > -- > > You received this message because you are subscribed to the Google > Groups "minikanren" group. > > To unsubscribe from this group and stop receiving emails from it, send > an email to [email protected] <javascript:>. > > To post to this group, send email to [email protected] > <javascript:>. > > Visit this group at https://groups.google.com/group/minikanren. > > For more options, visit https://groups.google.com/d/optout. > -- You received this message because you are subscribed to the Google Groups "minikanren" group. 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