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• Are there arrays in Latex(not asking for the way to typeset them but to use for programing)

  - by drasto

  Are there arrays in Latex ? I don't mean the way to typeset arrays. I mean arrays as the data structure in latex/tex as a "programming language". I need to store a number of vbox-es or hbox-es in array. Or it may by something like "an array of macros". More details: I have an environment that should typeset songs. I need to store some songs paragraphs given as arguments to my macro \songparagraph(so I will not typeset them, just store those paragraphs). As I don't know how many paragraphs can by in one particular song I need an array for this... When the environment is closed all the paragraphs will be typeset - but they will be first measured and the best placement for each paragraph will be computed(for example, some paragraphs can be put one aside other in two columns to make the song look more compact and save some space). Any ides would be welcome. Please if you know about that there are some arrays in latex post a link to some basic documentation, tutorial or just state basic commands.

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• Lazy Sequences that "Look Ahead" for Project Euler Problem 14

  - by ivar

  I'm trying to solve Project Euler Problem 14 in a lazy way. Unfortunately, I may be trying to do the impossible: create a lazy sequence that is both lazy, yet also somehow 'looks ahead' for values it hasn't computed yet. The non-lazy version I wrote to test correctness was: (defn chain-length [num] (loop [len 1 n num] (cond (= n 1) len (odd? n) (recur (inc len) (+ 1 (* 3 n))) true (recur (inc len) (/ n 2))))) Which works, but is really slow. Of course I could memoize that: (def memoized-chain (memoize (fn [n] (cond (= n 1) 1 (odd? n) (+ 1 (memoized-chain (+ 1 (* 3 n)))) true (+ 1 (memoized-chain (/ n 2))))))) However, what I really wanted to do was scratch my itch for understanding the limits of lazy sequences, and write a function like this: (def lazy-chain (letfn [(chain [n] (lazy-seq (cons (if (odd? n) (+ 1 (nth lazy-chain (dec (+ 1 (* 3 n))))) (+ 1 (nth lazy-chain (dec (/ n 2))))) (chain (+ n 1)))))] (chain 1))) Pulling elements from this will cause a stack overflow for n2, which is understandable if you think about why it needs to look 'into the future' at n=3 to know the value of the tenth element in the lazy list because (+ 1 (* 3 n)) = 10. Since lazy lists have much less overhead than memoization, I would like to know if this kind of thing is possible somehow via even more delayed evaluation or queuing?

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• Perl+Image::Magick usage: how to assemble several areas in one image into a new image?

  - by Jin

  Hi Everybody, I'm new to ImageMagick and haven't figured out how to assemble several areas into a new image. E.g., I know the "geometry" of words "hello" and "world" respectively in an image, what I need to do is to retrieve the word images and put then into one line image while keep their relative positions. Question1: Suppose I use the perl API, how should I use Composite() or other correct methods to do this? my $geom = sprintf('%dx%x+%d+%d', $word->{width}, $word->{height}, $offsetx, $offsety); $x = $lineimg->Composite($wordimg, $geom); warn "$x" if "$x"; Suppose $lineimg's size is big enough to hold all word images and the geometry has been computed. This code gives out a complain by ImageMagick: Exception 410: composite image required `Image::Magick' @ Magick.xs/XS_Image__Magick_Mogrify/7790 ... Question2: currently I only know how to crop a word image out of the original one and then Clone() method to restore the original image. Is there a way to copy instead of crop a specific area from a image? This way can save the time to copy back and forth the whole image several times. Does anybody know how to write this kind of processing? I appreciate all your help and suggestions! -Jin

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• Improving the performance of XSL

  - by Rachel

  I am using the below XSL 2.0 code to find the ids of the text nodes that contains the list of indices that i give as input. the code works perfectly but in terms for performance it is taking a long time for huge files. Even for huge files if the index values are small then the result is quick in few ms. I am using saxon9he Java processor to execute the XSL. <xsl:variable name="insert-data" as="element(data)*"> <xsl:for-each-group select="doc($insert-file)/insert-data/data" group-by="xsd:integer(@index)"> <xsl:sort select="current-grouping-key()"/> <data index="{current-grouping-key()}" text-id="{generate-id( $main-root/descendant::text()[ sum((preceding::text(), .)/string-length(.)) ge current-grouping-key() ][1] )}"> <xsl:copy-of select="current-group()/node()"/> </data> </xsl:for-each-group> </xsl:variable> In the above solution if the index value is too huge say 270962 then the time taken for the XSL to execute is 83427ms. In huge files if the index value is huge say 4605415, 4605431 it takes several minutes to execute. Seems the computation of the variable "insert-data" takes time though it is a global variable and computed only once. Should the XSL be addessed or the processor? How can i improve the performance of the XSL.

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• TSQL - make a literal float value

  - by David B

  I understand the host of issues in comparing floats, and lament their use in this case - but I'm not the table author and have only a small hurdle to climb... Someone has decided to use floats as you'd expect GUIDs to be used. I need to retrieve all the records with a specific float value. sp_help MyTable -- Column_name Type Computed Length Prec -- RandomGrouping float no 8 53 Here's my naive attempt: --yields no results SELECT RandomGrouping FROM MyTable WHERE RandomGrouping = 0.867153569942739 And here's an approximately working attempt: --yields 2 records SELECT RandomGrouping FROM MyTable WHERE RandomGrouping BETWEEN 0.867153569942739 - 0.00000001 AND 0.867153569942739 + 0.00000001 -- 0.867153569942739 -- 0.867153569942739 In my naive attempt, is that literal a floating point literal? Or is it really a decimal literal that gets converted later? If my literal is not a floating point literal, what is the syntax for making a floating point literal? EDIT: Another possibility has occurred to me... it may be that a more precise number than is displayed is stored in this column. It may be impossible to create a literal that represents this number. I will accept answers that demonstrate that this is the case. EDIT: response to DVK. TSQL is MSSQLServer's dialect of SQL. This script works, and so equality can be performed deterministically between float types: DECLARE @X float SELECT top 1 @X = RandomGrouping FROM MyTable WHERE RandomGrouping BETWEEN 0.839110948199148 - 0.000000000001 AND 0.839110948199148 + 0.000000000001 --yields two records SELECT * FROM MyTable WHERE RandomGrouping = @X I said "approximately" because that method tests for a range. With that method I could get values that are not equal to my intended value. The linked article doesn't apply because I'm not (intentionally) trying to straddle the world boundaries between decimal and float. I'm trying to work with only floats. This isn't about the non-convertibility of decimals to floats.

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• Scrollbars in ScrollView not showing after custom child view changes size

  - by Ted Hopp

  I have a ScrollView containing a client that is a vertical LinearLayout. The client, in turn, contains custom views that change height dynamically as a background thread does some work. The problem I'm having is that the ScrollView's vertical scroll bar is not updating correctly in Android 1.5. The most common problem occurs when the initial total height of the client is less than the viewport and grows. Initially there is no scroll bar, and it does not show up when the client grows until I actually scroll the window with a touch gesture or other UI action. After that, the scroll bar shows up. However, the thumb does not update as the height continues to change from the background thread. If I scroll the view again through the UI, the thumb immediately corrects itself. My code for updating the height from the background thread is: post(mLayoutRequestor); postInvalidate(); (mLayoutRequestor is a Runnable that just calls requestLayout().) This is done after I've recorded the new height in a variable mHeight. My onMeasure() method calls setMeasuredDimension with a height computed like this: private int measureHeight(int measureSpec) { int result; int specMode = MeasureSpec.getMode(measureSpec); int specSize = MeasureSpec.getSize(measureSpec); if (specMode == MeasureSpec.EXACTLY) { result = specSize; } else { result = mHeight; if (specMode == MeasureSpec.AT_MOST && result > specSize) result = specSize; } return result; } Am I supposed to be calling something else besides requestLayout() to get the scroll bar to update correctly?

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• How do calculators work with precision?

  - by zoul

  Hello! I wonder how calculators work with precision. For example the value of sin(M_PI) is not exactly zero when computed in double precision: #include <math.h> #include <stdio.h> int main() { double x = sin(M_PI); printf("%.20f\n", x); // 0.00000000000000012246 return 0; } Now I would certainly want to print zero when user enters sin(p). I can easily round somewhere on 1e–15 to make this particular case work, but that’s a hack, not a solution. When I start to round like this and the user enters something like 1e–20, they get a zero back (because of the rounding). The same thing happens when the user enters 1/10 and hits the = key repeatedly — when he reaches the rounding treshold, he gets zero. And yet some calculators return plain zero for sin(p) and at the same time they can work with expressions such as (1e–20)/10 comfortably. Where’s the trick?

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• Find all CSS rules that apply to an element

  - by Carl Byström

  Many tools/APIs provide ways of selecting elements of specific classes or IDs. There's also possible to inspect the raw stylesheets loaded by the browser. However, for browsers to render an element, they'll compile all CSS rules (possibly from different stylesheet files) and apply it to the element. This is what you see with Firebug or the WebKit Inspector - the full CSS inheritance tree for an element. How can I reproduce this feature in pure JavaScript without requiring additional browser plugins? Perhaps an example can provide some clarification for what I'm looking for: <style type="text/css"> p { color :red; } #description { font-size: 20px; } </style> <p id="description">Lorem ipsum</p> Here the p#description element have two CSS rules applied: a red color and a font size of 20 px. I would like to find the source from where these computed CSS rules originate from (color comes the p rule and so on).

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• How do you verify that 2 copies of a VB 6 executable came from the same code base?

  - by Tim Visher

  I have a program under version control that has gone through multiple releases. A situation came up today where someone had somehow managed to point to an old copy of the program and thus was encountering bugs that have since been fixed. I'd like to go back and just delete all the old copies of the program (keeping them around is a company policy that dates from before version control was common and should no longer be necessary) but I need a way of verifying that I can generate the exact same executable that is better than saying "The old one came out of this commit so this one should be the same." My initial thought was to simply MD5 hash the executable, store the hash file in source control, and be done with it but I've come up against a problem which I can't even parse. It seems that every time the executable is generated (method: Open Project. File Make X.exe) it hashes differently. I've noticed that Visual Basic messes with files every time the project is opened in seemingly random ways but I didn't think that would make it into the executable, nor do I have any evidence that that is indeed what's happening. To try to guard against that I tried generating the executable multiple times within the same IDE session and checking the hashes but they continued to be different every time. So that's: Generate Executable Generate MD5 Checksum: md5sum X.exe > X.md5 Verify MD5 for current executable: md5sum -c X.md5 Generate New Executable Verify MD5 for new executable: md5sum -c X.md5 Fail verification because computed checksum doesn't match. I'm not understanding something about either MD5 or the way VB 6 is generating the executable but I'm also not married to the idea of using MD5. If there is a better way to verify that two executables are indeed the same then I'm all ears. Thanks in advance for your help!

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• caching previous return values of procedures in scheme

  - by Brock

  In Chapter 16 of "The Seasoned Schemer", the authors define a recursive procedure "depth", which returns 'pizza nested in n lists, e.g (depth 3) is (((pizza))). They then improve it as "depthM", which caches its return values using set! in the lists Ns and Rs, which together form a lookup-table, so you don't have to recurse all the way down if you reach a return value you've seen before. E.g. If I've already computed (depthM 8), when I later compute (depthM 9), I just lookup the return value of (depthM 8) and cons it onto null, instead of recursing all the way down to (depthM 0). But then they move the Ns and Rs inside the procedure, and initialize them to null with "let". Why doesn't this completely defeat the point of caching the return values? From a bit of experimentation, it appears that the Ns and Rs are being reinitialized on every call to "depthM". Am I misunderstanding their point? I guess my question is really this: Is there a way in Scheme to have lexically-scoped variables preserve their values in between calls to a procedure, like you can do in Perl 5.10 with "state" variables?

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• Jqplot - How to have vertical lines and make xaxis go up in plotted values?

  - by Beginner

  I have plotted a line graph using jqplot. What i would like is vertical lines and to start from 3 and go up in the plotted values along the bottom. so 3, 6, 9, 12 , 15, 29, 36 Also a dash marker along the left. This is what i have at the moment: $(document).ready(function(){ $.jqplot('chart2', [[[3, @(Model.LearnerWeek[0])], [6, @(Model.LearnerWeek[1])], [9, @(Model.LearnerWeek[2])], [12, @(Model.LearnerWeek[3])], [15, @(Model.LearnerWeek[4])], [29, @(Model.LearnerWeek[5])], [36, @(Model.LearnerWeek[6])]], [[3, @(Model.ManagerWeek[0])], [6, @(Model.ManagerWeek[1])], [9, @(Model.ManagerWeek[2])], [12, @(Model.ManagerWeek[3])], [15, @(Model.ManagerWeek[4])], [29, @(Model.ManagerWeek[5])], [36, @(Model.ManagerWeek[6])]]], { axes: { yaxis: { tickOptions: { show: false}, min: 0, max: 100, label: 'Participation Rate', labelRenderer: $.jqplot.CanvasAxisLabelRenderer }, xaxis: { min: 3, max: 36, label: 'Week', tickOptions: { formatString: '%d' } } }, seriesDefaults: { showMarker: false , rendererOptions: { diameter: undefined, // diameter of pie, auto computed by default. padding: 10, // padding between pie and neighboring legend or plot margin. fill: true, // render solid (filled) slices. shadowOffset: 2, // offset of the shadow from the chart. shadowDepth: 15, // Number of strokes to make when drawing shadow. Each stroke // offset by shadowOffset from the last. shadowAlpha: 1 // Opacity of the shadow } }, seriesColors: ['#3591cf', '#ef4058', '#73C774', '#C7754C', '#17BDB8'] }); }); I have played around with render options and xasis but cant seem to work it out

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• What kind of library to use for display of graphical objects and right click context menus

  - by Gopal

  Hi all, Goal: To develop a web based NMS interface which displays a network topology (e.g., switches, routers, links, endhosts). Each node should be 'movable' (draggable to an appropriate place manually or their best location computed algorithmically). I should be able to zoom into the network graph (say if there are many clusters of nodes and I want to concentrate on a particular cluster of nodes). I should be able to right-click any node or link and get a context menu (e.g., 'show routing table', 'show interfaces', 'show bandwidth utilization graph' etc.). The data for this network topology will be fetched by making calls to an apache based webserver where the backend scripts in python will fetch the appropriate data and send it via JSON to the web client. Question: I am assuming that some sort of javascript library/framework will be most appropriate for this - jQuery, Dojo, Moo etc. [I've never used any of these before]. Which of these would be most recommended for this sort of thing. Which would be easiest to learn (say in a months time). Thanks for any tips.

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• why i^=j^=i^=j isn't equal to *i^=*j^=*i^=*j

  - by klvoek

  In c , when there is variables (assume both as int) i less than j , we can use the equation i^=j^=i^=j to exchange the value of the two variables. For example, let int i = 3, j = 5; after computed i^=j^=i^=j, I got i = 5, j = 3 . What is so amazing to me. But, if i use two int pointers to re-do this , with *i^=*j^=*i^=*j , use the example above what i got will be i = 0 and j = 3. Then, describe it simply: In C 1 int i=3, j=5; i^=j^=i^=j; // after this i = 5, j=3 2 int i = 3, j= 5; int *pi = &i, *pj = &j; *pi^=*pj^=*pi^=*pj; // after this, $pi = 0, *pj = 5 In JavaScript var i=3, j=5; i^=j^=i^=j; // after this, i = 0, j= 3 the result in JavaScript makes this more interesting to me my sample code , on ubuntu server 11.0 & gcc #include <stdio.h> int main(){ int i=7, j=9; int *pi=&i, *pj=&j; i^=j^=i^=j; printf("i=%d j=%d\n", i, j); i=7, j==9; *pi^=*pj^=*pi^=*pj printf("i=%d j=%d\n", *pi, *pj); } however, i had spent hours to test and find out why, but nothing means. So, please help me. Or, just only i made some mistake???

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• python crc32 woes

  - by lazyr

  I'm writing a python program to extract data from the middle of a 6 GB bz2 file. A bzip2 file is made up of independently decryptable blocks of data, so I only need to find a block (they are delimited by magic bits), then create a temporary one-block bzip2 file from it in memory, and finally pass that to the bz2.decompress function. Easy, no? The bzip2 format has a crc32 checksum for the file at the end. No problem, binascii.crc32 to the rescue. But wait. The data to be checksummed does not necessarily end on a byte boundary, and the crc32 function operates on a whole number of bytes. My plan: use the binascii.crc32 function on all but the last byte, and then a function of my own to update the computed crc with the last 1-7 bits. But hours of coding and testing has left me bewildered, and my puzzlement can be boiled down to this question: how come crc32("\x00") is not 0x00000000? Shouldn't it be, according to the wikipedia article? You start with 0b00000000 and pad with 32 0's, then do polynomial division with 0x04C11DB7 until there are no ones left in the first 8 bits, which is immediately. Your last 32 bits is the checksum, and how can that not be all zeroes? I've searched google for answers and looked at the code of several crc32 implementations without finding any clue to why this is so.

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• Can piping of screen to file change the result of a C++ code?

  - by Biga

  I am having this very weird behaviour with a C++ code: It gives me different results when running with and without piping the screen to a file (reproducible in cygwin and linux). I mean, if I get the same executable and run it like './run' or run it like './run out.log', I get different results! I use std::cout to output to screen, all lines ending with endl; I use ifstream for the input file; I use ofstream for output, all lines ending with endl. I am using g++ 4. Any idea what is going on? UPDATE: I have hard-coded the input data, so 'ifstream' is not used, and problem persists. UPDATE 2: That's getting interesting. I have output three variables that are computed initially, and that's what I get with and without piping direct to screen: 0 -0.02 0 piped: 0 -0.02 1.04083e-17 So there's a round-off difference with and without piping the output! Now, why piping would interefere with an internal computation of the code?

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• Java: fastest way to do random reads on huge disk file(s)

  - by cocotwo

  I've got a moderately big set of data, about 800 MB or so, that is basically some big precomputed table that I need to speed some computation by several orders of magnitude (creating that file took several mutlicores computers days to produce using an optimized and multi-threaded algo... I do really need that file). Now that it has been computed once, that 800MB of data is read only. I cannot hold it in memory. As of now it is one big huge 800MB file but splitting in into smaller files ain't a problem if it can help. I need to read about 32 bits of data here and there in that file a lot of time. I don't know before hand where I'll need to read these data: the reads are uniformly distributed. What would be the fastest way in Java to do my random reads in such a file or files? Ideally I should be doing these reads from several unrelated threads (but I could queue the reads in a single thread if needed). Is Java NIO the way to go? I'm not familiar with 'memory mapped file': I think I don't want to map the 800 MB in memory. All I want is the fastest random reads I can get to access these 800MB of disk-based data. btw in case people wonder this is not at all the same as the question I asked not long ago: http://stackoverflow.com/questions/2346722/java-fast-disk-based-hash-set

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• Load page for validation but do not display it to user in ASP.NET

  - by Kevin

  We have a site requiring users pay $2 to view the details of a record. We occasionally get complaints because we send them to the payment page, and once they pay it turns out the record isn't valid, or it was lost, or the data couldn't be generated. So we want to add in a check to ensure the page constructs properly before the user is required to pay for it. However, we don't want the user to have access to the page until they pay for it. Is there anything in ASP.NET 3.5 or just general web design that would allow something like this? The data on the record is real time and computed on a backend server before sent to the client. Occasionally this computation fails for whatever reason. Our alternative is to call all of the loading methods and validate the data, then redirect them to the payment page. The problem is A) this will be a relatively involved process rewriting all of these methods to return validation information, and B) it still doesn't guarentee us the page will load properly. Any thoughts?

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• Can FFT length affect filtering accuracy?

  - by Charles

  Hi, I am designing a fractional delay filter, and my lagrange coefficient of order 5 h(n) have 6 taps in time domain. I have tested to convolute the h(n) with x(n) which is 5000 sampled signal using matlab, and the result seems ok. When I tried to use FFT and IFFT method, the output is totally wrong. Actually my FFT is computed with 8192 data in frequency domain, which is the nearest power of 2 for 5000 signal sample. For the IFFT portion, I convert back the 8192 frequency domain data back to 5000 length data in time domain. So, the problem is, why this thing works in convolution, but not in FFT multiplication. Does converting my 6 taps h(n) to 8192 taps in frequency domain causes this problem? Actually I have tried using overlap-save method, which perform the FFT and multiplication with smaller chunks of x(n) and doing it 5 times separately. The result seems slight better than the previous, and at least I can see the waveform pattern, but still slightly distorted. So, any idea where goes wrong, and what is the solution. Thank you.

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• Can redirection of screen output to file change the result of a C++ code?

  - by Biga

  I am having this very weird behaviour with a C++ code: It gives me different results when running with and without redirecting the screen output to a file (reproducible in cygwin and linux). I mean, if I get the same executable and run it like ./run or run it like ./run >out.log, I get different results! I use std::cout to output to screen, all lines ending with endl; I use ifstream for the input file; I use ofstream for output, all lines ending with endl. I am using g++ 4. Any idea what is going on? UPDATE: I have hard-coded the input data, so 'ifstream' is not used, and problem persists. UPDATE 2: That's getting interesting. I have probed three variables that are computed initially, and that's what I get when using with and without redirecting the output to file redirected to file: 0 -0.02 0 direct to screen: 0 -0.02 1.04083e-17 So there's a round-off difference in the code variables with and without redirecting the output! Now, why redirecting would interefere with an internal computation of the code? UPDATE 3: If I redirect to /dev/null, I get the sam behaviour as outputing direct to screen, instead of redirecting to file.

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• HMAC URLs instead of login?

  - by Tres

  In implementing my site (a Rails site if it makes any difference), one of my design priorities is to relieve the user of the need to create yet another username and password while still providing useful per-user functionality. The way I am planning to do this is: User enters information on the site. Information is associated with the user via server-side session. User completes entering information, server sends an access URL via e-mail to the user roughly in the form of: http://siteurl/<user identifier>/<signature: HMAC(secret + salt + user identifier)> User clicks URL, site looks up user ID and salt and computes the HMAC with the server-stored secret and authenticates if the computed HMAC and signature match. My question is: is this a reasonably secure way to accomplish what I'm looking to do? Are there common attacks that would render it useless? Is there a compelling reason to abandon my desire to avoid a username/password? Is there a must-read book or article on the subject? Note that I'm not dealing with credit card numbers or anything exceedingly private, but I would still like to keep the information reasonably secure.

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• My kernel only works in block (0,0)

  - by ZeroDivide

  I am trying to write a simple matrixMultiplication application that multiplies two square matrices using CUDA. I am having a problem where my kernel is only computing correctly in block (0,0) of the grid. This is my invocation code: dim3 dimBlock(4,4,1); dim3 dimGrid(4,4,1); //Launch the kernel; MatrixMulKernel<<<dimGrid,dimBlock>>>(Md,Nd,Pd,Width); This is my Kernel function __global__ void MatrixMulKernel(int* Md, int* Nd, int* Pd, int Width) { const int tx = threadIdx.x; const int ty = threadIdx.y; const int bx = blockIdx.x; const int by = blockIdx.y; const int row = (by * blockDim.y + ty); const int col = (bx * blockDim.x + tx); //Pvalue stores the Pd element that is computed by the thread int Pvalue = 0; for (int k = 0; k < Width; k++) { Pvalue += Md[row * Width + k] * Nd[k * Width + col]; } __syncthreads(); //Write the matrix to device memory each thread writes one element Pd[row * Width + col] = Pvalue; } I think the problem may have something to do with memory but I'm a bit lost. What should I do to make this code work across several blocks?

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• How can I efficiently manipulate 500k records in SQL Server 2005?

  - by cdeszaq

  I am getting a large text file of updated information from a customer that contains updates for 500,000 users. However, as I am processing this file, I often am running into SQL Server timeout errors. Here's the process I follow in my VB application that processes the data (in general): Delete all records from temporary table (to remove last month's data) (eg. DELETE * FROM tempTable) Rip text file into the temp table Fill in extra information into the temp table, such as their organization_id, their user_id, group_code, etc. Update the data in the real tables based on the data computed in the temp table The problem is that I often run commands like UPDATE tempTable SET user_id = (SELECT user_id FROM myUsers WHERE external_id = tempTable.external_id) and these commands frequently time out. I have tried bumping the timeouts up to as far as 10 minutes, but they still fail. Now, I realize that 500k rows is no small number of rows to manipulate, but I would think that a database purported to be able to handle millions and millions of rows should be able to cope with 500k pretty easily. Am I doing something wrong with how I am going about processing this data? Please help. Any and all suggestions welcome.

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• Data structure to build and lookup set of integer ranges

  - by actual

  I have a set of uint32 integers, there may be millions of items in the set. 50-70% of them are consecutive, but in input stream they appear in unpredictable order. I need to: Compress this set into ranges to achieve space efficient representation. Already implemented this using trivial algorithm, since ranges computed only once speed is not important here. After this transformation number of resulting ranges is typically within 5 000-10 000, many of them are single-item, of course. Test membership of some integer, information about specific range in the set is not required. This one must be very fast -- O(1). Was thinking about minimal perfect hash functions, but they do not play well with ranges. Bitsets are very space inefficient. Other structures, like binary trees, has complexity of O(log n), worst thing with them that implementation make many conditional jumps and processor can not predict them well giving poor performance. Is there any data structure or algorithm specialized in integer ranges to solve this task?

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• How can I dynamically set the default namespace declaration of an XSLT transformation's output XML?

  - by Paralife

  I can do it, but not for the default namespace, using the <xsl:namespace>. If I try to do it for the default namespace: <xsl:namespace name="" select"myUri"/> it never works. It demands that I explicitly define the namespace of the element to be able to use the above null prefix declaration. The reason I want this is because I have a task to transform an input XML file to another output xml. The output XML has many elements and i dont want to have to explicitly set the namespace for every element. Thats why I want to set the default and never bother again. But the default must be computed from some data in the source XML. It does not change during the whole transformation, but it is dependent on input XML data. Any solution? EDIT 1: To sup up: I want to create a namespace dynamically and set it to be the default namespace of the output xml document. The uri of the namespace is derived from some data in the input XML. If I use <xsl:namespace> in my root output element, I cannot create a default namespace for it, only a prefixed one. And even with the prefixed one, it does not propagate to children.

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• suggestions on syntax to express mathematical formula concisely

  - by aaa

  hello. I am developing functional domain specific embedded language within C++ to translate formulas into working code as concisely and accurately as possible. I post prototype in the comment, it is about 2 hundred lines long. Right now my language looks something like this (well, actually is going to look like): // implies two nested loops j=0:N, i=0,j (range(i) < j < N)[T(i,j) = (T(i,j) - T(j,i))/e(i+j)]; // implies summation over above expression sum(range(i) < j < N))[(T(i,j) - T(j,i))/e(i+j)]; I am looking for possible syntax improvements/extensions or just different ideas about expressing mathematical formulas as clearly and precisely as possible (in any language, not just C++). Can you give me some syntax examples relating to my question which can be accomplished in your language of choice which consider useful. In particular, if you have some ideas about how to translate the above code segments, I would be happy to hear them. Thank you just to clarify and give actual formula, my short-term goal is to express the following expression concisely where values in <> are already computed as 4-dimensional array

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