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bio website haiqus.com
location Chicago, IL
age 28
visits member for 2 years, 10 months
seen Nov 29 at 22:16

Software engineer using Ruby, JRuby, Go, and the Unix toolbox.


Jul
8
comment What does Simmons mean by “closure” in this exercise?
Yes, I see now that $A=S$ and $B=T$. He write in my copy "$g \circ f$ is a closure operation on $A$ [sic]." Is that too a typo, or am I misunderstanding something more fundamental in this exercise?
Jul
6
comment What does Simmons mean by “closure” in this exercise?
I think the Wikipedia article mentioned by @QiaochuYuan answers the question. A closure of X gives you the smallest set containing X. So, g(f) gives us the smallest set containing a select element of A, and f(g) gives us the smallest set containing a select element of B. They're both closures, and more to the point, they're adjoints in the category.
Jul
6
asked What does Simmons mean by “closure” in this exercise?
May
28
awarded  Autobiographer