BSL uses special syntax information (installed by beginner:define) to only allow applications on first-order functions. For example,<div><br></div><div>(define (f a)</div><div> (a 1))</div><div><br></div><div>is an error in BSL. The way this is detected is that every top-level define (like for 'f') has a special notation on it that says "I'm a function". Since 'a' doesn't have this, then the macro for app in BSL can throw an error.</div> <div><br></div><div>The main thing that this macro does is give that information to the identifiers, but you need to redefine them, which causes the need for the variant mapping since type-case is looking for the original variant names.</div> <div><br></div><div>Jay</div><div><br></div><div class="gmail_extra"><br><br><div class="gmail_quote">On Mon, Nov 5, 2012 at 6:13 AM, Prabhakar Ragde <span dir="ltr"><<a href="mailto:plragde@uwaterloo.ca" target="_blank">plragde@uwaterloo.ca</a>></span> wrote:<br> <blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div class="im">On 2012-11-05 6:43 AM, Matthew Flatt wrote:<br> <br> <blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"> Here's a first cut at a module that you can import into BSL programs.<br> <br> The least obvious part is defining a new `define-type' and `type-case'<br> that invents hidden names for the variants and them maps between them<br> while expanding to the original forms.<br> </blockquote> <br></div> Wow, thanks. I will study the code and do my best to understand it, and test it for deployment next fall. I can already see the outline of how your code achieves what you describe, but could you please say a few words about why that's necessary, to improve my understanding of BSL? Thanks again. --PR<div class="HOEnZb"> <div class="h5"><br> ____________________<br> Racket Users list:<br> <a href="http://lists.racket-lang.org/users" target="_blank">http://lists.racket-lang.org/<u></u>users</a><br> </div></div></blockquote></div><br><br clear="all"><div><br></div>-- <br>Jay McCarthy <<a href="mailto:jay@cs.byu.edu" target="_blank">jay@cs.byu.edu</a>><br>Assistant Professor / Brigham Young University<br><a href="http://faculty.cs.byu.edu/~jay" target="_blank">http://faculty.cs.byu.edu/~jay</a><br> <br>"The glory of God is Intelligence" - D&C 93<br> </div>