Interview with the authors of An Invitation to Applied Category Theory: Seven Sketches in Compositionality

I recently listened to this interview with the Brendan Fong and David Spivak, authors of  'An Invitation to Applied Category Theory: Seven Sketches in Compositionality', currently one of my favorite books. The interviewer, Cory Brunson, is excellent and I particularly appreciated the way he got the authors to explain the key ideas of the various chapters.  For anyone starting out on the book (or on the course) this interview would make a good introduction.

Indeed the whole New Books Network looks very interesting.

Hamster ball fixes network problem

One Saturday morning a year or two ago my wife complained that she couldn't get 'onto' her emails.  She said this had happened several times in the previous few days but only when she was using the computer in the living room.  This computer was connected to our modem router by an Ethernet cable and inspection showed that the cable had been nibbled where it ran along the floor.  My wife admitted that she had been allowing our hamster to run free in the living room while I was at work.  I went out and bought a replacement cable. My wife went out and bought a hamster ball.  The connection problems did not occur again.

Category Theory without Objects

Our notion of category is that of [Eilenberg & Mac Lane, 1945]. We identify objects with their identity maps and we regard a diagram A--f-->B as a formula which asserts that A is the (identity map of the) domain of f and that B is the (identity map of the) codomain of f.

From the start of the PhD thesis of F. William Lawvere ( Functorial Semantics of Algebraic Theories and Some Algebraic Problems in the context of Functorial Semantics of Algebraic Theories, 1963).

Alloy Talk

Here is a good recent talk by Jay Parlar on using the Alloy Analyzer to find bugs in software designs.

Seasonal variation in the numbers of Phaonia subventa

I have written a little script to help me create plots showing the seasonal variation in the numbers of various species of fly I have collected.

Most species show a large peak in numbers in late spring or early summer with none or very few in winter.  The Muscid fly Phaonia subventa is unusual in showing fewer flies in the summer than in the winter.  I had noticed that it was one of the most common woodland flies in winter (I have seen them on Christmas day morning, sunning themselves on tree trunks when the temperature was below 5C) but I hadn't realised, until I saw the above plot, that they seem to almost completely disappear during the summer months. This might be a consequence of the dry summers we have had in the south of England in the past few years.

My script is still a bit primitive (it is written in Gnu Awk!) and I intend to tidy it up and extend it (and maybe rewrite it in Rust).  But if you are interested you can find a copy in the Github repository where I store the catalog of my fly collection (https://github.com/tristrambrelstaff/flies).  The script is mplot.awk.