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Brent Yorgey
Works at University of Pennsylvania
Attends University of Pennsylvania
Lives in Philadelphia, PA
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"Hold my jacket!  HOLD MY JACKET!!"
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Our paper has been accepted for the 2015 Mathematics of Program Construction Conference:

Polynomial Functors Constrained by Regular Expressions
http://dept.cs.williams.edu/~byorgey/pub/type-matrices.pdf

It's based on some blog posts from a couple of years ago and shows how to define a tree type in a language like Haskell where the leaves of the tree are constrained to match a regular expression. A basic example that many are familiar with is the type of lists where the elements alternate between two types. The picture corresponds to an example of a binary tree with regular expression b*1a* where 1 is the type with just one inhabitant so it functions as a "hole". These types have the property that it's completely impossible to build a tree that fails to satisfy the constraint.

As a side effect it also shows how you can think of Conor McBride's Jokers and Clowns paper as really being about divided differences (ie. (f(x)-f(y))/(x-y)) applied to types, even though you can't literally divide types: https://personal.cis.strath.ac.uk/conor.mcbride/Dissect.pdf

Sadly it's hard to find a programming language that can truly automate this process, especially as it involves matrices whose entries are types. Brent and I both tried independently with Agda, but even with dependent types we got stuck. But that doesn't stop you using the paper to hand craft the appropriate type. (I guess Template Haskell would work fine but that's cheating.)
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Very nice paper!
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My third game of Go with Noah (3 yrs =)
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View from our new front door.
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A technician? I thought Google would deliver a self-decorating door in a self-driving car.
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Have him in circles
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You'll have to host a Haskell symposium there!!
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Unfortunately, 'cum laude' differs highly per country. E.g. in The Netherlands 'cum laude' is the only distinction and is awarded to ~5-10% of PhDs. Germany follows the usual three distinctions of the Latin system (cum laude, magna cum laude, summa cum laude). tl;dr: in The Netherlands cum laude is the highest distinction, in Germany summa is the highest distinction and you probably want to get at least cum laude.

Though, I am not sure if this applies to 'with honours' to, if it is less ambiguous, that would be something :).
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Noah's favorite game right now is to sing "A,B,C,D,E,F,____" where the __ is filled in with anything other than "G" (e.g. "Q", but more often non-letters such as "cow", "lobster", "seven", "climb").  Whereupon I tickle him in mock outrage and he shrieks with laughter.  I'm very proud that my son finds type errors humorous.
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Teach him 123456789ABCDEF0.
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Me: "Noah, are you ready to get out of the bath now?"
Noah: "Not no. Yes!"

I should have given him a stern lecture about the dangers of double negation elimination, but I was blinded by the cuteness.
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Perhaps that was the point. Not only is it refutable that he wasn't ready to get out of the bath, it was also provable that he was.
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When I picked up Noah from daycare yesterday, he wanted to go to the potty before we left for home.  I then discovered he needed his diaper changed first.  But it turned out his diaper bag was downstairs.  So we had to get his diaper bag in order to change his diaper in order to go to the potty in order to go home.  On the way down the stairs I taught him about the ways of the world.  "We are shaving yaks, buddy," I said. "Saving ax," he repeated.
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Pros and cons of having monsters on your plate.  Pro: sometimes the monsters talk to you.  Con: sometimes sauce gets on the monsters.
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Have him in circles
966 people
Björn Buckwalter's profile photo
Sebastian Korten's profile photo
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AlonzoAndKeya Us's profile photo
Anish Kumar's profile photo
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Currently
Philadelphia, PA
Previously
Washington, DC - Williamstown, MA
Work
Occupation
PhD student
Employment
  • University of Pennsylvania
    PhD student, 2008 - present
Education
  • University of Pennsylvania
    Computer Science, 2008 - present
  • Williams College
    Computer Science, 2000 - 2004
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Male
Birthday
January 10
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Married