De Bruijn also invented De Bruijn indices for handling bound variables in lambda calculus without having to deal with renaming. De Bruijn indices are used to implement practically every modern functional programming language. They are also quite beautiful. http://en.wikipedia.org/wiki/De_Bruijn_index
I learned about why De Bruijn indices are awesome just a couple of days after his death--very unfortunate timing. I only learned about it after I started appreciating them...
(Basically, they are neat because they let you represent a lambda as just a body and an environment as just a list of values, elegantly avoiding the pitfalls of using named variables.)
I first heard about de Bruijn sequences [1] in a talk by Persi Diaconis. Among other things, he described the lock picking "use" listed first in the Wikipedia article. They're such obviously cool objects, that I feel like they should be useful in all sorts of places. Sadly I've yet to find an excuse to use them myself though.
People might be confused or bewildered by the depth of this mans research. How does esoteric math apply to everyday life?!?!?
Well,De Bruijn Graphs are used every day to assemble short pieces of DNA into newly sequenced genomes. They build the relationships to build the genome.
I got an email from him back in late October (I had previously sent an email asking about his work in mathematical models of the brain though I didn't really expect a reply), apparently his main computer had recently broke down at that time and he didn't have access to everything he had stored on it. I wonder if the data was recovered. I'm really sad and depressed he's gone.
