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seen Aug 29 at 1:44

Aug
15
awarded  Pundit
Aug
10
comment Mathematical software wish list
It's very likely that this would necessarily be almost as creative as a mathematician. Note how difficult it is to train humans to do this task: almost all of them who we successfully train to being able to assess math articles, also reach the epsilon-higher level of being able to generate some.
Aug
10
comment Mathematical software wish list
Isn't this more or less pinch-to-zoom as found on touchscreens? Just for the special case where the starting points of the two fingers are two corners of the viewport.
Aug
10
comment Mathematical software wish list
To try to put in one sentence what Thomas wants, for non-readers of German: just as many programs allow one to zoom in by drawing a rectangle in the current viewport over the part one wants to zoom in on, one should be able to zoom out by drawing a rectangle to show which part of viewport should contain the current image.
Jun
27
comment Inherent ambiguity of the context-sensitive language $L = {a^ib^ic^id^je^jf^j \bigcap a^ib^jc^id^je^if^j} $ or $a^nb^nc^nd^ne^nf^n$
@XL_at_China, WorldCat says there are copies of both of those books in the National Library of China; perhaps that is accessible to you?
Jun
26
comment Inherent ambiguity of the context-sensitive language $L = {a^ib^ic^id^je^jf^j \bigcap a^ib^jc^id^je^if^j} $ or $a^nb^nc^nd^ne^nf^n$
I personally don't know of a good definition of a parse for a context-sensitive grammar, and it seems you need that if you want to define ambiguity as having multiple parses (is there another way to define ambiguity?). It might be interesting to look at less powerful grammars (e.g. conjunctive grammars) with a clear definition of a parse.
May
9
awarded  Popular Question
Aug
17
revised Most memorable titles
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Aug
17
awarded  Nice Answer
Jun
25
awarded  Yearling
Jun
7
awarded  Nice Question
Oct
14
comment Awfully sophisticated proof for simple facts
While this is obviously overkill, the general technique is so useful that perhaps students should see this proof -- when cardinality is introduced, it's not immediately obvious just how useful it is. For example, even before saying what a computer program is (but knowing that they are specified by strings), one can deduce that there are uncomputable sets, and similarly non-regular languages, etc. I'd say the general idea is that we often have countably many descriptions (programs, grammars, restrictions to $\mathbf{Q}$) but uncountably many objects, so most objects cannot be described.
Sep
27
comment Open?: Bpp VS EXP^NP
I'm not an expert, and maybe I'm having a dumb moment, but isn't BPP easily shown to be in EXP by simulating all possible coin flips?
Jun
21
comment Open problems with monetary rewards
Knuth says his cheques are much more often cached than cashed.
May
5
comment What is the easiest randomized algorithm to motivate to the layperson?
This algorithm is more obviously correct than Buffon's needle, though.
May
1
answered What would you want to see at the Museum of Mathematics?
May
1
revised What would you want to see at the Museum of Mathematics?
deleted 25 characters in body
Apr
20
comment German mathematical terms like “Nullstellensatz”
I always assumed $U$ was for subspaces because you call a topological space $T$ for topological space, and when you take a subspace of it, you just take the next letter.
Apr
4
comment What are the most misleading alternate definitions in taught mathematics?
The $A$ is not needed, but it makes the presentation of inverse functions more symmetrical and allows one to define partial functions with fixed domains so that functions are partial functions.
Apr
4
comment What are the most misleading alternate definitions in taught mathematics?
Another problem with this definition is that it's wrong -- in modern mathematics (though less so in the informal language of some analysts, IME) a function has a codomain. Under this definition a function has an image, but any superset of the image could be its domain. As an undergraduate, I was given this definition several times, and it bothered me. A function is a triple $(A, B, R)$ where R is a subset of $A\times B$ such that...