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  • Confused about GNU `sort(1)` of a numerical sub field

    - by Chen Levy
    I wish to sort a space separated table, with the numerical value that found on the 2nd field. I can assume that the 2nd field is always fooN but the length of N is unknown: antiq. foo11 girls colleaguing foo2 Leinsdorf Cousy foo0 Montgomeryville bowlegged foo1 pollack Chevrier foo10 ill-conceived candlebomb foo3 seventieths autochthony foo101 re-enable beneficiate foo100 osteometric I read man sort(1) and played with all sort of options. On my system I found the line: sort -n -k2.5 table to work. My question is why? According to the man page: -k, --key=POS1[,POS2] start a key at POS1, end it at POS 2 (origin 1) ... POS is F[.C][OPTS], where F is the field number and C the characterposition in the field. OPTS is one or more single-letter ordering options, which override global ordering options for that key. If no key is given, use the entire line as the key. So why sort -n -k2.4 table don't work and sort -n -k.5 does?

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  • Does Len function only evaluate numerical results?

    - by Mel
    Why does the following code not output "Error" if the form is submitted with a blank field? Does Len only evaluate numerical values? <cfif NOT Len(Trim("Form.myField"))> <cfoutput>Error</cfoutput> </cfif> The following also does not evaluate as expected: <cfif Len(Trim("Form.myField")) IS 0> <cfoutput>Error</cfoutput> </cfif> HTML: <input type="text" name="myField" value="">

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  • Using an int as the numerical representation of a string in C#

    - by bluewall21
    I'm trying to use an integer as the numerical representation of a string, for example, storing "ABCD" as 0x41424344. However, when it comes to output, I've got to convert the integer back into 4 ASCII characters. Right now, I'm using bit shifts and masking, as follows: int value = 0x41424344; string s = new string ( new char [] { (char)(value >> 24), (char)(value >> 16 & 0xFF), (char)(value >> 8 & 0xFF), (char)(value & 0xFF) }); Is there a cleaner way to do this? I've tried various casts, but the compiler, as expected, complained about it.

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  • php: fopen() of an URL breaks for domain names, not for numerical addresses

    - by b0fh
    After hours of trying to debug a third-party application having trouble with fopen(), i finally discovered that php -r 'echo(file_get_contents("http://www.google.com/robots.txt"));' fails, but php -r 'echo(file_get_contents("http://173.194.32.81/robots.txt"));' Succeeds. Note that as the webserver user, I can ping www.google.com and it resolves just fine. I straced both executions of PHP, and they diverge like this: For the numerical v4 URL: socket(PF_INET, SOCK_STREAM, IPPROTO_IP) = 3 fcntl(3, F_GETFL) = 0x2 (flags O_RDWR) fcntl(3, F_SETFL, O_RDWR|O_NONBLOCK) = 0 connect(3, {sa_family=AF_INET, sin_port=htons(80), sin_addr=inet_addr("173.194 poll([{fd=3, events=POLLOUT}], 1, 0) = 0 (Timeout) ...[bunch of poll/select/recvfrom]... close(3) = 0 For the domain name: socket(PF_INET6, SOCK_DGRAM, IPPROTO_IP) = 3 close(3) = 0 PHP didn't even try to do anything with that socket, it seems. Or even resolve the domain, for that matter. WTF ? Recompiling PHP with or without ipv6 support did not seem to matter. Disabling ipv6 on this system is not desirable. Gentoo Linux, PHP 5.3.14, currently giving a try to PHP 5.4 and see if it helps. Anyone has an idea ? EDIT: php -r 'echo gethostbyname("www.google.com");' Works and yield an ipv4, while php -r 'echo(file_get_contents("http://[2a00:1450:4007:803::1011]/"));' Seems to return a blank result. EDIT 2: I didn't even notice the first time, that the v6 socket opened when the name is used is a SOCK_DGRAM.

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  • Algorithms for finding a numerical record in a list of ordered numbers

    - by Ankur
    I have a list of incomplete ordered numbers. I want to find a particular number with as few steps as possible. Are there any improvements on this algorithm, I assume you can count the set size without difficulty - it will be stored and updated every time a new item is added. Your object is to get your cursor over the value x The first number (smallest) is s, and the last number (greatest) is g. Take the midpoint m1 of the set: calculate is x < m1, If yes then s <= x < m1 If no then m1 < x <= g If m1 = x then you're done. Keep repeating till you find x. Basically dividing the set into two parts with each iteration till you hit x. The purpose is to retrieve a numerical id from a very large table to then find the associated other records. I would imagine this is the most trivial kind of indexing available, are there improvements?

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  • Convert a Dynamic[] construct to a numerical list

    - by Leo Alekseyev
    I have been trying to put together something that allows me to extract points from a ListPlot in order to use them in further computations. My current approach is to select points with a Locator[]. This works fine for displaying points, but I cannot figure out how to extract numerical values from a construct with head Dynamic[]. Below is a self-contained example. By dragging the gray locator, you should be able to select points (indicated by the pink locator and stored in q, a list of two elements). This is the second line below the plot. Now I would like to pass q[[2]] to a function, or perhaps simply display it. However, Mathematica treats q as a single entity with head Dynamic, and thus taking the second part is impossible (hence the error message). Can anyone shed light on how to convert q into a regular list? EuclideanDistanceMod[p1_List, p2_List, fac_: {1, 1}] /; Length[p1] == Length[p2] := Plus @@ (fac.MapThread[Abs[#1 - #2]^2 &, {p1, p2}]) // Sqrt; test1 = {{1.`, 6.340196001221532`}, {1.`, 13.78779876355869`}, {1.045`, 6.2634018978377295`}, {1.045`, 13.754947081416544`}, {1.09`, 6.178367702583522`}, {1.09`, 13.72055251752498`}, {1.135`, 1.8183153704413153`}, {1.135`, 6.082497198000075`}, {1.135`, 13.684582525399742`}, {1.18`, 1.6809452373465104`}, {1.18`, 5.971583107298081`}, {1.18`, 13.646996905469383`}, {1.225`, 1.9480537697339537`}, {1.225`, 5.838386922625636`}, {1.225`, 13.607746407088161`}, {1.27`, 2.1183174369679234`}, {1.27`, 5.669799095595362`}, {1.27`, 13.566771130126131`}, {1.315`, 2.2572975468163463`}, {1.315`, 5.444014254828522`}, {1.315`, 13.523998701347882`}, {1.36`, 2.380307009155079`}, {1.36`, 5.153024664297602`}, {1.36`, 13.479342200528283`}, {1.405`, 2.4941312539733285`}, {1.405`, 4.861423833512566`}, {1.405`, 13.432697814928654`}, {1.45`, 2.6028066447609426`}, {1.45`, 4.619367407525507`}, {1.45`, 13.383942212133244`}}; DynamicModule[{p = {1.2, 10}, q = {1.3, 11}}, q := Dynamic@ First@test1[[ Ordering[{#, EuclideanDistanceMod[p, #, {1, .1}]} & /@ test1, 1, #1[[2]] < #2[[2]] &]]]; Grid[{{Show[{ListPlot[test1, Frame -> True, ImageSize -> 300], Graphics@Locator[Dynamic[p]], Graphics@ Locator[q, Appearance -> {Small}, Background -> Pink]}]}, {Dynamic@p}, {q},{q[[2]]}}]]

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  • Retain numerical precision in an R data frame?

    - by David
    When I create a dataframe from numeric vectors, R seems to truncate the value below the precision that I require in my analysis: data.frame(x=0.99999996) returns 1 (see update 1) I am stuck when fitting spline(x,y) and two of the x values are set to 1 due to rounding while y changes. I could hack around this but I would prefer to use a standard solution if available. example Here is an example data set d <- data.frame(x = c(0.668732936336141, 0.95351462456867, 0.994620622127435, 0.999602102672081, 0.999987126195509, 0.999999955814133, 0.999999999999966), y = c(38.3026509783688, 11.5895099585560, 10.0443344234229, 9.86152339768516, 9.84461434575695, 9.81648333804257, 9.83306725758297)) The following solution works, but I would prefer something that is less subjective: plot(d$x, d$y, ylim=c(0,50)) lines(spline(d$x, d$y),col='grey') #bad fit lines(spline(d[-c(4:6),]$x, d[-c(4:6),]$y),col='red') #reasonable fit Update 1 Since posting this question, I realize that this will return 1 even though the data frame still contains the original value, e.g. > dput(data.frame(x=0.99999999996)) returns structure(list(x = 0.99999999996), .Names = "x", row.names = c(NA, -1L), class = "data.frame") Update 2 After using dput to post this example data set, and some pointers from Dirk, I can see that the problem is not in the truncation of the x values but the limits of the numerical errors in the model that I have used to calculate y. This justifies dropping a few of the equivalent data points (as in the example red line).

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  • Parsing basic math equations for children's educational software?

    - by Simucal
    Inspired by a recent TED talk, I want to write a small piece of educational software. The researcher created little miniature computers in the shape of blocks called "Siftables". [David Merril, inventor - with Siftables in the background.] There were many applications he used the blocks in but my favorite was when each block was a number or basic operation symbol. You could then re-arrange the blocks of numbers or operation symbols in a line, and it would display an answer on another siftable block. So, I've decided I wanted to implemented a software version of "Math Siftables" on a limited scale as my final project for a CS course I'm taking. What is the generally accepted way for parsing and interpreting a string of math expressions, and if they are valid, perform the operation? Is this a case where I should implement a full parser/lexer? I would imagine interpreting basic math expressions would be a semi-common problem in computer science so I'm looking for the right way to approach this. For example, if my Math Siftable blocks where arranged like: [1] [+] [2] This would be a valid sequence and I would perform the necessary operation to arrive at "3". However, if the child were to drag several operation blocks together such as: [2] [\] [\] [5] It would obviously be invalid. Ultimately, I want to be able to parse and interpret any number of chains of operations with the blocks that the user can drag together. Can anyone explain to me or point me to resources for parsing basic math expressions? I'd prefer as much of a language agnostic answer as possible.

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  • Finding the intersection of two vector equations.

    - by Matthew Mitchell
    I've been trying to solve this and I found an equation that gives the possibility of zero division errors. Not the best thing: v1 = (a,b) v2 = (c,d) d1 = (e,f) d2 = (h,i) l1: v1 + ?d1 l2: v2 + µd2 Equation to find vector intersection of l1 and l2 programatically by re-arranging for lambda. (a,b) + ?(e,f) = (c,d) + µ(h,i) a + ?e = c + µh b +?f = d + µi µh = a + ?e - c µi = b +?f - d µ = (a + ?e - c)/h µ = (b +?f - d)/i (a + ?e - c)/h = (b +?f - d)/i a/h + ?e/h - c/h = b/i +?f/i - d/i ?e/h - ?f/i = (b/i - d/i) - (a/h - c/h) ?(e/h - f/i) = (b - d)/i - (a - c)/h ? = ((b - d)/i - (a - c)/h)/(e/h - f/i) Intersection vector = (a + ?e,b + ?f) Not sure if it would even work in some cases. I haven't tested it. I need to know how to do this for values as in that example a-i. Thank you.

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  • Solving simultaneous equations

    - by Milo
    Here is my problem: Given x, y, z and ratio where z is known and ratio is known and is a float representing a relative value, I need to find x and y. I know that: x / y == ratio y - x == z What I'm trying to do is make my own scroll pane and I'm figuring out the scrollbar parameters. So for example, If the scrollbar must be able to scroll 100 values (z) and the thumb must consume 80% of the bar (ratio = 0.8) then x would be 400 and y would be 500. Thanks

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  • Formatting equations in LaTeX

    - by jetsam
    When I include an equation in LaTeX that is enumerated, i.e. {\begin{equation} $$ $$ ... \end{equation} } The line above the equation (blank space between the text preceeding it and the equation) is huge. How do I make it smaller?

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  • Typical Applications of Linear System Solver in Game Developemnt

    - by craftsman.don
    I am going to write a custom solver for linear system. I would like to survey the typical problems involved the linear system solving in games. So that I can custom optimization on these problems based on the shape of the matrix. currently I am focus on these problems: B-Spline editing (I use a linear solve to resolve the C0, C1, C2 continuity) Constraint in Simulation (especially Position-Constraint, cloth) Both of them are Banded Matrix. I want to hear about some other applications of a linear system in games. Thank you.

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  • Integration error in high velocity

    - by Elektito
    I've implemented a simple simulation of two planets (simple 2D disks really) in which the only force is gravity and there is also collision detection/response (collisions are completely elastic). I can launch one planet into orbit of the other just fine. The collision detection code though does not work so well. I noticed that when one planet hits the other in a free fall it speeds backward and goes much higher than its original position. Some poking around convinced me that the simplistic Euler integration is causing the error. Consider this case. One object has a mass of 1kg and the other has a mass equal to earth. Say the object is 10 meters above ground. Assume that our dt (delta t) is 1 second. The object goes to the height of 9 meters at the end of the first iteration, 7 at the end of the second, 4 at the end of the third and 0 at the end of the fourth iteration. At this points it hits the ground and bounces back with the speed of 10 meters per second. The problem is with dt=1, on the first iteration it bounces back to a height of 10. It takes several more steps to make the object change its course. So my question is, what integration method can I use which fixes this problem. Should I split dt to smaller pieces when velocity is high? Or should I use another method altogether? What method do you suggest? EDIT: You can see the source code here at github:https://github.com/elektito/diskworld/

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  • HTML numerical to UTF

    - by Teneke
    How can i convert this $langClarContent = &# 1059.,ч.,и.,&# 1090.,&# 1077.,&# 1083.,Dokeos &# 1077., &# 1089.,&# 1080.,&# 1089.,&# 1090.,&# 1077.,&# 1084., &# 1079.,&# 1072., &# 1091.,&# 1087.,&# 1088.,&# 1072.,&# 1074.,&# 1091.,&# 1074.,&# 1072.,&# 1114.,е., &# 1089.,о., &# 1091.,&# 1095.,&# 1077.,&# 1114.,&# 1077., &# 1080., &# 1079.,&# 1085.,&# 1072.,е.,&# 1114.,&# 1077.,. &# 1058.,&# 1086.,&# 1112., &# 1080.,м., &# 1076.,&# 1086.,&# 1087.,&# 1091.,&# 1096.,&# 1090.,&# 1072., &# 1085.,&# 1072., у.,&# 1095 to an utf related answer like $langClarContent = Учител Dokeos е систем за управување со учење и знаење. Тој им допушта на уч

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  • Fuzzy Search on Material Descriptions including numerical sizes & general descriptions of material t

    - by Kyle
    We're looking to provide a fuzzy search on an electrical materials database (i.e. conduit, cable, etc.). The problem is that, because of a lack of consistency across all material types, we could not split sizes into separate fields from the text description because some materials are rated by things other than size. I've attempted a combination of a full text search & a SQL CLR implementation of the Levenshtein search algorithm (for assistance in ranking), but my results are a little funky (i.e. they are not sorting correctly due to improper ranking). For example, if the search term is "3/4" ABCD Conduit", I'll might get back several irrelevant results in the following order: 1/2" Conduit 1/4" X 3/4" Cable 1/4" Cable Ties 3/4" DFC Conduit Tees 3/4" ABCD Conduit 3/4" Conduit I believe I've nailed the problem down to the fact that these two search algorithms do not factor in the relevance of punctuation & numeric. That is, in such a search, I'd expect the size to take precedence over any fuzzy match on the rest of the description, but my results don't reflect that. My question is: Can anyone recommend better search algorithms or different approaches that may be better suited for searching a combination of alphanumerics & punctuation characters?

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  • Numerical precision of double type in Visual C++ 2008 Express debugger

    - by damik
    I'm using Visual C++ 2008 Express Edition and when i debug code: double x = 0.2; I see in debugging tooltip on x 0.20000000000000001 but: typedef numeric_limits< double > double_limit; int a = double_limit::digits10 gives me: a = 15 Why results in debugger are longer than maybe ? What is this strange precision based on ? My CPU is Intel Core 2 Duo T7100

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  • Mobile web - hidden numerical input

    - by user499846
    Hi I am writing a web app (mainly iphone targeted) where the user has to enter their dob as part of the log in, I need this to be <input type = 'password'however I also want to enable the numeric section of the keyboard. I would usually change the type attr to 'number' however as this needs to be hidden I wondered if there was another way to activate the numeric pad Cheers! (ps I do not want to use any frameworks such as jquery on this)

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  • numerical computation locks up ruby

    - by kolosy
    i'm trying to implement an id obfuscation scheme, with a simple hash borrowed elsewhere. i've added a method on the application helper: @@M_ID = 2**31-1 @@PRIME = 1580030173 @@PRIME_INVERSE = 59260789 # (calculated from MAXID and PRIME offline) def obfuscate_id(x) if x return ((x * @@PRIME) & @@M_ID) else x end end for some reason, whenever this is called, ruby locks up, and starts eating up disk space on my mac... like - gigs of it. any ideas?

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  • Easy Slider 1.7 - Show any numerical slide as next

    - by Yourbudweiser
    I am using Easy Slider 1.7 - jQuery plugin and have made many modifications. My slider contains 7 slides, numeric navigation and next and previous arrows. The only problem is the numeric navigation. When you are on slide 1 and click slide 5, for example, all the slides scroll by, one-by-one. I am having trouble modifying the code so that whatever slide you are on, when you click another slide, it is the next one. Sample here: http://www.weiserwebworld.com/slider.html

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