11,024 reputation
2453
bio website vyznev.net
location Helsinki, Finland
age
visits member for 3 years, 7 months
seen 10 hours ago

I'm a PhD student in biomathematics, working on stochastic individual-based models of evolution in spatially structured populations. My other interests include cryptography, programming games and puzzles, photography and graphic design.

I started programming (in AmigaBASIC) when I was 10 years old. Nowadays, I'm most comfortable using Perl, C and JavaScript. I know Java and PHP too, but I can't really say I like them. I also know some Python, but not as much as I'd like.


CC-Zero Please consider any (original) code I post to Stack Overflow and other Stack Exchange sites to be released under CC-Zero unless stated otherwise. You may do whatever you want with it and don't have to credit me in any way, although of course that would be nice.


I'm the main author and maintainer of the Stack Overflow Unofficial Patch (SOUP), a user script for browsers with GreaseMonkey-compatible user script support (Firefox, Chrome, Opera, possibly Safari) that fixes or works around a number of outstanding issues with the Stack Exchange user interface.

I tend to answer a lot more questions than I ask. Some answers I'm rather proud of:


Nov
22
comment Square root of a divergent series diverges.
@martycohen: Technically, you only get $\ge$, not $>$, since $a_n = 0 \implies a_n \to 0$.
Nov
18
awarded  Sportsmanship
Nov
17
comment Most ambiguous and inconsistent phrases and notations in maths
@Prateek: If you find that annoying, I bet you'll really hate things like $\frac{\rm d}{{\rm d}x}x^2=2x$ (since, if you insisted on assigning a value to $x$ and evaluating from the inside out, you'd end up with something totally nonsensical like $\frac{\rm d}{{\rm d}5}25=10$). It makes more sense if you allow "unevaluated expressions in one or more variables" as first-class objects in your mathematical framework (and not just when buried inside function definitions). If you don't, you'll have to go for something like $f\in O(n\mapsto n^2)$ to make asymptotical notation rigorous.
Nov
16
comment n balls into n holes with exactly one hole remaining empty
@Carl: All three answers are identical: $n(n-1)(n-2)! = \binom{n}{1}(n-1)! = n(n-1)! = n!$.
Nov
16
answered Does a continuous point-wise limit imply uniform convergence?
Nov
16
comment Does a continuous point-wise limit imply uniform convergence?
@RudytheReindeer: That's probably the simplest example, yes, but any sequence of continuous functions satisfying the criteria given by Mike will work. For example, if you'd like your functions to be not just continuous but $C^\infty$, there are bump functions that will do the trick.
Nov
11
comment Subtracting Quarters of Squares Equals Multiply?!
@Joao:   works well, too.
Nov
11
revised Subtracting Quarters of Squares Equals Multiply?!
replace mathjax filler with  
Nov
10
comment Is inclusion map not the same as identity?
@Asaf: While that definition has some merit, if you don't include the codomain as part of the definition, you can't speak of surjectivity as an intrinsic property of the function. (You can, of course, still speak of a function being "surjective over the set $B$".)
Nov
1
comment Why are there letters as additional digits in bases greater than the decimal base (10)?
@DanielFischer: That's the price of having the numeric and alphabetic character ranges neatly aligned in blocks of 16 and 32 characters -- you get some awkward spare slots at the ends of the ranges that need to be filled with more or less random punctuation. On the other hand, the decision to align the ranges like that meant that conversion between uppercase and lowercase letters and control codes (and between decimal digits and their numeric values) could be implemented by simple bit flipping, without the need for more complicated addition circuits.
Oct
25
awarded  Enlightened
Oct
25
awarded  Nice Answer
Oct
21
revised Explain $x^{x^{x^{{\cdots}}}} = \,\,3$
simpler dots
Oct
21
comment How can I calculate this limit without using L'Hopital's rule?
-1 for a title that's totally indistinguishable from the dozens of similar questions shown in the sidebar.
Oct
13
comment How to do limits approaching infinity with trig?
@Kaaagome: No, this method will not work for "every trig limit to infinity problem". (That's such a broad class of problems that I'm pretty sure there is no single general trick that would work for all of them.) For example, applying $|\sin x|\le1$ won't help you with $\lim_{x\to\infty} x\sin\frac1x$ (although, using $|\sin x|\le|x|$, you can at least get an upper bound). Still, it's a useful trick (e.g.) whenever you have a bounded (or slow-growing) function divided by function that monotonely tends to infinity.
Oct
13
comment How to do limits approaching infinity with trig?
In fact, we don't need the first (trivial) inequality at all; $|f(x)| \le 1/x$ (for $x > 0$) is equivalent to $-1/x \le f(x) \le 1/x$, and then we can apply the squeeze lemma as $x\to\infty$.
Oct
11
answered Can the distance between two points equals zero
Oct
6
revised A continuous function defined on an interval can have a mean value. What about a median?
added 306 characters in body
Oct
6
comment A continuous function defined on an interval can have a mean value. What about a median?
-1, I do not believe this is a reasonable definition of the median of a function. In particular, let $f(x) = 7$ over the interval $[0,1]$; by your definition, the median of $f$ would be $\frac12$, when by any (IMO) sensible definition it should be $7$.
Oct
6
answered A continuous function defined on an interval can have a mean value. What about a median?