> On Jun 1, 2016, at 7:22 AM, [email protected] 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 [email protected]. > 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 [email protected]. For more options, visit https://groups.google.com/d/optout.
