> On Jun 1, 2016, at 7:22 AM, lfacc...@jhu.edu wrote: > > Hi, all, and authors of SEwPR in particular. > > I believe Exercise 15.1 has the following problems: > > 1. The function passed to the Y combinator should have an parameter > before `x' called `tri'. > > 2. `ifz' is not a construct in ISWIM as presented in the previous > chapters. I could extend the language to support it, of course, but I > think this does not contribute to the goal of the exercise. Instead, > I think it should use `iszero'. > > Summing up the previous two points, the code looks like: > > ((Y (λ tri (λ x > (((iszero x) > (λ y 0)) > (λ y (+ x (tri (- x 1)))))))) > 3)
You’re absolutely correct. Surprisingly, this part of the book is actually constructed in such a way that when ‘make’ is run, it runs almost every fragment of code in the source to make sure it’s working Redex code. I fail to understand why this isn’t done here, but I can’t say until we investigate the source. Thanks for the report. We will post this on our errata page. What name should we use to acknowledge you? — Matthias > > ----- > > Let me take the opportunity to thank the authors for the book, PLT Redex > and Racket. The more I learn, the more I appreciate the effort you put > into them. > > Best. > > -- > You received this message because you are subscribed to the Google Groups > "Racket Users" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to racket-users+unsubscr...@googlegroups.com. > For more options, visit https://groups.google.com/d/optout. -- You received this message because you are subscribed to the Google Groups "Racket Users" group. To unsubscribe from this group and stop receiving emails from it, send an email to racket-users+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
