<html><head></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><div><br></div>The Indiana school of macrology in the early 1980s. Eugene, Bruce, and I used this to teach macros to undergrads but Dan Friedman may have implicitly formulated them before Eugene sketched them out and Bruce and I wrote them down. <div><br><div><br><div><div>On Jan 9, 2014, at 1:45 AM, Ben Duan wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite"><div dir="ltr">What is the source of <span style="color:rgb(0,0,0);font-family:arial,sans-serif;font-size:13px"> "</span><span class="" style="font-family:arial,sans-serif;font-size:13px">three</span><span style="color:rgb(0,0,0);font-family:arial,sans-serif;font-size:13px"> </span><span class="" style="font-family:arial,sans-serif;font-size:13px">canonical </span><span style="color:rgb(0,0,0);font-family:arial,sans-serif;font-size:13px"></span><span class="" style="font-family:arial,sans-serif;font-size:13px">categories</span><span style="color:rgb(0,0,0);font-family:arial,sans-serif;font-size:13px">"?</span><div>
<span style="color:rgb(0,0,0);font-family:arial,sans-serif;font-size:13px"><br></span></div><div><span style="color:rgb(0,0,0);font-family:arial,sans-serif;font-size:13px">Thanks,</span></div><div><span style="color:rgb(0,0,0);font-family:arial,sans-serif;font-size:13px">Ben</span></div>
<div class="gmail_extra"><br><br><div class="gmail_quote">On Sat, Nov 23, 2013 at 2:46 PM, John Clements <span dir="ltr"><<a href="mailto:clements@brinckerhoff.org" target="_blank">clements@brinckerhoff.org</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">I'm preparing a 10-minute lightning talk on hygienic macros in rust (preview: I'm barely going to *mention* hygiene), and in the process, I've been surveying some of the Rust macros, and roughly categorizing them in terms of the "three canonical categories" that Matthias described--apologies if I'm misrepresenting him/you:<br>
- changing evaluation order,<br>
- implementing a data sublanguage, and<br>
- creating new binding forms.<br>
<br>
Some of the Rust macros seem to fall into a fourth category, which arises from the fact that certain things are not expressions:<br>
<br>
- abstracting over things that are not expressions.<br>
<br>
For instance:<br>
<br>
cmp_impl!(impl Eq, eq, ne)<br>
cmp_impl!(impl TotalEq, equals)<br>
cmp_impl!(impl Ord, lt, gt, le, ge)<br>
cmp_impl!(impl TotalOrd, cmp -> cmp::Ordering)<br>
<br>
Each of these expands into a top-level "impl" declaration, extending implementations of, e.g., Ord, from type T to type Ratio<T>.<br>
<br>
More generally, it seems to me that every time you constrain first-class-ness by making things not-first-class (e.g. module-level stuff in Racket), you will be required to use macros to abstract over these things.<br>
<br>
Thoughts?<br>
<br>
Back to writing my talk...<br>
<br>
John<br>
<br>
<br>
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</blockquote></div><br></div></div>
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