In addition, I plan to scan the next chapter (Functor), and send it over to those willing to go ahead with studying the book and doing the exercises. I got a feeling that our discussions will be way more productive if we are on the same level: meaning that it would be better to discuss monadic stuff after we are sure functors, natural transformations, and also maybe adjointness and limits are firmly established notions - but of course these are cool areas anyway, initial algebras for specific Haskell monads etc, so probably it makes sense to share time, giving space to both.<br>
<br><div class="gmail_quote">2010/2/12 Jason Dusek <span dir="ltr"><<a href="mailto:jason.dusek@gmail.com">jason.dusek@gmail.com</a>></span><br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
The meeting was held in the Alonzo Church classroom. Tea cakes<br>
(chocolate & banana bread) and almonds were served. Next time,<br>
I'll bring some decent tea.<br>
<br>
<br>
Attending: Vlad, Mikael, myself, Nicholas, Ian & Rebecca.<br>
<br>
<br>
The meeting opened with some material from the text: a simple<br>
problem on functors and a discussion of the "map-lifting<br>
property".<br>
<br>
<br>
I brought up comonadic IO for discussion but little progress<br>
was made.<br>
<br>
<br>
Nicholas wished to talk about type specifications and how we<br>
use them for correctness in functional programming. We<br>
discussed the specific examples of trees.<br>
<br>
<br>
Vlad sketched out a tree datatype and mentioned that it should<br>
be a poset, too. Mikael objected to this and objected to<br>
calling these rooted datatypes trees. Turns out in graph<br>
theory, trees are a different thing:<br>
<br>
<a href="http://en.wikipedia.org/wiki/Tree_%28graph_theory%29" target="_blank">http://en.wikipedia.org/wiki/Tree_%28graph_theory%29</a><br>
<br>
The tree data structure of CS fame is an "arborescence" to<br>
graph theorists:<br>
<br>
<a href="http://en.wikipedia.org/wiki/Arborescence_%28graph_theory%29" target="_blank">http://en.wikipedia.org/wiki/Arborescence_%28graph_theory%29</a><br>
<br>
There was also some discussion of pointers and identity.<br>
<br>
<br>
Really, though, Nicholas's ideas about specification involved<br>
a notion of functors and so we came back to those. Vlad and<br>
Mikael presented on the list monad and fixed points were<br>
briefly introduced.<br>
<br>
<br>
Somewhere in all this, Ian mentioned he had to go. We all<br>
opted to leave at that point. Vlad and I will continue on in<br>
Chapter 3, "Functors", and do a few problems.<br>
<br>
--<br>
Jason Dusek<br>
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</font></blockquote></div><br><br clear="all"><br>-- <br>Thanks,<br>-Vlad<br>