I have to change my past DW/LJ links at some point so that they don't all break. But that's going to take work and time, so I can't do that just yet!

(New URL is, as I've mentioned, http://sqentropy.ax.lt/ )

### Class things

May. 13th, 2014 10:46 amWe were on the subject of inverse functions, and the professor showed us how to find the derivative of an inverse function without knowing what that inverse function actually is. (This was in the multivariate case, but the logic holds both there and if you have only one variable.)

But then I started thinking: couldn't this be used to find the inverse function itself? Just repeat finding the derivative for the second, third, fourth, etc, derivative and then construct a Taylor series. And I asked about this, and he said that, indeed, that was possible.

One of the nice things about mathematics is that if you're not violating any of the premises, any trick you can think of will work. There's no god of mathematics that simply says "now you're just being a smartass" :)

(Later, he dealt with the theory of finding a graph curve (y = f(a, b, c, ...)) for a more general function (that inputs and outputs a vector), in the vicinity of a point. He proved that the curve will always exist given certain preconditions, but not how to find it. So I asked how one may find it, and he said that "in general, you'll have to do it numerically. There may be closed-form tricks in certain special cases, but I don't know of them". I later thought that sounded a lot like integration: there are tricks but if you want something fully general, numerical is the way to go :) )

### (no subject)

May. 1st, 2014 04:41 pmI'm migrating my host from dyndns (since they're planning on charging). I should update past post links, but for now, use http://sqentropy.ax.lt/ where you used to use http://sqentropy.dyndns.org/ .

[EDIT: And obviously this goes for my mail address as well. Change @sqentropy.dyndns.org into @sqentropy.ax.lt .]

### And then for some programming

Apr. 6th, 2014 11:49 pmI will say this, however: The functional programming I'm learning about (not what I had a test in) seems to be coloring my thoughts pretty significantly at the moment, because I used some of today's time wondering how to make a C-alike language that would support a more functional style... and I came up with odd syntax like

`void foo(int x, int y) = { cout << x << ", " << y << endl; }`

("And all functions are simply variables in the global scope") and

void bar() = { void foo(int a) = { return(a + 1); } int an_array[3] = {1, 2, 3}; // increments every element in an_array by 1. imperative_map(an_array, foo, 3); for (int i = 0; i < 3; ++i) { cout << a_list[i] << endl; } }

But there might be a language that does this already. Though to be powerful enough, this hypothetical C variant should also support type inference, so that higher order functions like imperative_map can work on any and all types. Either that, or it's typename<T> time!

Er, yeah.

**( Read more... )**

### (no subject)

Feb. 20th, 2014 08:46 pm*it's the un-Lembas*.

Where Lembas is supposed to be filling, this is mostly air. You end up wondering whether you actually ate anything! It's quite snacklike in that respect.

It's not bad, though. It's just... weird, which I guess is its appeal :)

(And I think I've come to like unusual things more, lately.)

**blackvoiddragon**showed me these corvids:

http://imgur.com/r/aww/iXrac3T

http://jonathandevil.tumblr.com/post/

and http://memoirs-of-blanche.tumblr.com/

:)

### Tests done!

Dec. 19th, 2013 10:13 am(Though I always will be doing

*something*, even if that is writing weird things here, or making fractal renderers for fun.)

Somehow, I feel quite tired, though. Perhaps I should try not to burden my mind too much, since I have been burdening it quite a bit on the preparations for the finals. But that's easier said than done, because I

*like*using my mind. We'll see how that goes - I know I should rest a bit, but the tiredness itself makes it harder to do the right kind of decisions, so there's some element of positive feedback there.

As for the subjects I had tests in, there were three: mathematics (mostly calculus), numerical analysis (including plain old differential equations), and basic scientific programming. I think I did best at programming, then mathematics, then analysis. Amusingly enough, it was not so much the computer parts of numerical analysis that got me down as the mathematical ones (e.g. analytically solving linear and separable ODEs). I know the logic, but knowing the logic isn't enough: I also have to practice it, and I hadn't done that enough.

The only error I think I made on the programming thing was thinking that a Python

`dict`is a primitive and so clones when you do an assignment of the type

`x = y`. Call-by-sharing languages that exempt some types (but not all) from being references go against my aesthetics (for inconsistency purposes - but I've said so before) and I suppose it's only fitting that what snagged me was that particular feature :)

### Coding question

Dec. 3rd, 2013 11:59 pmWhat do you think would be most interesting to learn about - functional programming or GPGPU programming? I know just about the same amount about each.

(I'm

*leaning*in one direction, but still haven't quite decided.)