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• Downsampling and applying a lowpass filter to digital audio

  - by twk

  I've got a 44Khz audio stream from a CD, represented as an array of 16 bit PCM samples. I'd like to cut it down to an 11KHz stream. How do I do that? From my days of engineering class many years ago, I know that the stream won't be able to describe anything over 5500Hz accurately anymore, so I assume I want to cut everything above that out too. Any ideas? Thanks. Update: There is some code on this page that converts from 48KHz to 8KHz using a simple algorithm and a coefficient array that looks like { 1, 4, 12, 12, 4, 1 }. I think that is what I need, but I need it for a factor of 4x rather than 6x. Any idea how those constants are calculated? Also, I end up converting the 16 byte samples to floats anyway, so I can do the downsampling with floats rather than shorts, if that helps the quality at all.

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• Math algorithm question

  - by Senica Gonzalez

  I'm not sure if this can be done without some determining factor....but wanted to see if someone knew of a way to do this. I want to create a shifting scale for numbers. Let's say I have the number 26000. I want the outcome of this algorithm to be 6500; or 25% of the original number. But if I have the number 5000, I want the outcome to be 2500; or 50% of the original number. The percentages don't have to be exact, this is just an example. I just want to have like a sine wave sort of thing. As the input number gets higher, the output number is a lower percentage of the input. Does that make sense?

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• How to use Page Object pattern with Cucumber and Webrat / Selenium?

  - by Will Sargent

  I'm looking at a cucumber test suite that is somewhat brittle right now; many small steps, and no knowledge of the page itself. I'd like to factor out the logic involved in the step definitions inside a series of Selenium PageObjects. As seen here. However, because I'm using Webrat and not Selenium, everything has to go through the Webrat model. So I cannot do class MyPage < Selenium::WebPage end because that adds a direct dependency. So I have to route everything through Webrat while still maintaining the Selenium Page object goodness. No documentation on this that I can see: if someone has anything on Webrat + PageModel I'd love to see it.

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• What one-time-password devices are compatible with mod_authn_otp?

  - by netvope

  mod_authn_otp is an Apache web server module for two-factor authentication using one-time passwords (OTP) generated via the HOTP/OATH algorithm defined in RFC 4226. The developer's has listed only one compatible device (the Authenex's A-Key 3600) on their website. If a device is fully compliant with the standard, and it allows you to recover the token ID, it should work. However, without testing, it's hard to tell whether a device is fully compliant. Have you ever tried other devices (software or hardware) with mod_authn_otp (or other open source server-side OTP program)? If yes, please share your experience :)

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• What software do you use for letter templating and printing?

  - by Pratik

  In our LOB application there is a very important use case of printing letters, which are then printed and posted out from a mail house (thousands per day). The current situation is that the letter templates are created in Word 97 and fields are mail merged from values in database using a VB.Net application that basically uses word automation. But depending on Word 97 is not a good idea today. We only have a couple of PCs that have Word 97 installed as rest of the company has moved to Office 2007. What software or technology (compatible with .Net) is available today that best suits this scenario. Is it better to do the same thing but move to Word 2007 or PDF or something else. Price may not be a factor. The important thing is that the letter templates must be designed by business users and data to fill placeholders come from DB. A bonus would be to import the hundreds of existing Word 97 letter templates without rewriting them from scratch.

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• being able to solve google code jam problem sets

  - by JPro

  This is not a homework question, but rather my intention to know if this is what it takes to learn programming. I keep loggin into TopCoder not to actually participate but to get the basic understand of how the problems are solved. But to my knowledge I don't understand what the problem is and how to translate the problem into an algorithm that can solve it. Just now I happen to look at ACM ICPC 2010 World Finals which is being held in china. The teams were given problem sets and one of them is this: Given at most 100 points on a plan with distinct x-coordinates, find the shortest cycle that passes through each point exactly once, goes from the leftmost point always to the right until it reaches the rightmost point, then goes always to the left until it gets back to the leftmost point. Additionally, two points are given such that the the path from left to right contains the first point, and the path from right to left contains the second point. This seems to be a very simple DP: after processing the last k points, and with the first path ending in point a and the second path ending in point b, what is the smallest total length to achieve that? This is O(n^2) states, transitions in O(n). We deal with the two special points by forcing the first path to contain the first one, and the second path contain the second one. Now I have no idea what I am supposed to solve after reading the problem set. and there's an other one from google code jam: Problem In a big, square room there are two point light sources: one is red and the other is green. There are also n circular pillars. Light travels in straight lines and is absorbed by walls and pillars. The pillars therefore cast shadows: they do not let light through. There are places in the room where no light reaches (black), where only one of the two light sources reaches (red or green), and places where both lights reach (yellow). Compute the total area of each of the four colors in the room. Do not include the area of the pillars. Input * One line containing the number of test cases, T. Each test case contains, in order: * One line containing the coordinates x, y of the red light source. * One line containing the coordinates x, y of the green light source. * One line containing the number of pillars n. * n lines describing the pillars. Each contains 3 numbers x, y, r. The pillar is a disk with the center (x, y) and radius r. The room is the square described by 0 = x, y = 100. Pillars, room walls and light sources are all disjoint, they do not overlap or touch. Output For each test case, output: Case #X: black area red area green area yellow area Is it required that people who program should be should be able to solve these type of problems? I would apprecite if anyone can help me interpret the google code jam problem set as I wish to participate in this years Code Jam to see if I can do anthing or not. Thanks.

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• How to put a newline into a column header in an xtable in R

  - by PaulHurleyuk

  I have a dataframe that I am putting into a sweave document using xtable, however one of my column names is quite long, and I would like to break it over two lines to save space calqc_table<-structure(list(RUNID = c(1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L), ANALYTEINDEX = c(1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L), ID = structure(1:11, .Label = c("Cal A", "Cal B", "Cal C", "Cal D", "Cal E", "Cal F", "Cal G", "Cal H", "Cal High", "Cal Low", "Cal Mid"), class = "factor"), mean_conc = c(200.619459644855, 158.264703128903, 102.469121407733, 50.3551544728544, 9.88296440865076, 4.41727762501703, 2.53494715706024, 1.00602831741361, 199.065054555735, 2.48063347296935, 50.1499780776199), sd_conc = c(2.3275711264554, NA, NA, NA, NA, NA, NA, 0.101636943231162, 0, 0, 0), nrow = c(3, 1, 1, 1, 1, 1, 1, 3, 2, 2, 2)), .Names = c("Identifier of the Run within the Study", "ANALYTEINDEX", "ID", "mean_conc", "sd_conc", "nrow"), row.names = c(NA, -11L ), class = "data.frame") calqc_xtable<-xtable(calqc_table) I have tried putting a newline into the name, but this didn't seem to work names(calqc_table)[1]<-"Identifier of the \nRun within the Study" Is there a way to do this ? I have seen someone suggest using the latex function from the hmisc package to manually iterate over the table and write it out in latex manually, including the newline, but this seems like a bit of a faf !

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• Remove first 'n' elements from list without itterating

  - by Eldhose M Babu

  I need an efficient way of removing items from list. If some condition happens, I need to remove first 'n' elements from a list. Can some one suggest the best way to do this? Please keep in mind: performance is a factor for me, so I need a faster way than itterating. Thanks. I'm thinking of a way through which the 'n'th item can be made as the starting of the list so that the 0-n items will get garbage collected. Is it possible?

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• Why are there 3 conflicting OpenCV camera calibration formulas?

  - by John

  I'm having a problem with OpenCV's various parameterization of coordinates used for camera calibration purposes. The problem is that three different sources of information on image distortion formulae apparently give three non-equivalent description of the parameters and equations involved: (1) In their book "Learning OpenCV…" Bradski and Kaehler write regarding lens distortion (page 376): xcorrected = x * ( 1 + k1 * r^2 + k2 * r^4 + k3 * r^6 ) + [ 2 * p1 * x * y + p2 * ( r^2 + 2 * x^2 ) ], ycorrected = y * ( 1 + k1 * r^2 + k2 * r^4 + k3 * r^6 ) + [ p1 * ( r^2 + 2 * y^2 ) + 2 * p2 * x * y ], where r = sqrt( x^2 + y^2 ). Assumably, (x, y) are the coordinates of pixels in the uncorrected captured image corresponding to world-point objects with coordinates (X, Y, Z), camera-frame referenced, for which xcorrected = fx * ( X / Z ) + cx and ycorrected = fy * ( Y / Z ) + cy, where fx, fy, cx, and cy, are the camera's intrinsic parameters. So, having (x, y) from a captured image, we can obtain the desired coordinates ( xcorrected, ycorrected ) to produced an undistorted image of the captured world scene by applying the above first two correction expressions. However... (2) The complication arises as we look at OpenCV 2.0 C Reference entry under the Camera Calibration and 3D Reconstruction section. For ease of comparison we start with all world-point (X, Y, Z) coordinates being expressed with respect to the camera's reference frame, just as in #1. Consequently, the transformation matrix [ R | t ] is of no concern. In the C reference, it is expressed that: x' = X / Z, y' = Y / Z, x'' = x' * ( 1 + k1 * r'^2 + k2 * r'^4 + k3 * r'^6 ) + [ 2 * p1 * x' * y' + p2 * ( r'^2 + 2 * x'^2 ) ], y'' = y' * ( 1 + k1 * r'^2 + k2 * r'^4 + k3 * r'^6 ) + [ p1 * ( r'^2 + 2 * y'^2 ) + 2 * p2 * x' * y' ], where r' = sqrt( x'^2 + y'^2 ), and finally that u = fx * x'' + cx, v = fy * y'' + cy. As one can see these expressions are not equivalent to those presented in #1, with the result that the two sets of corrected coordinates ( xcorrected, ycorrected ) and ( u, v ) are not the same. Why the contradiction? It seems to me the first set makes more sense as I can attach physical meaning to each and every x and y in there, while I find no physical meaning in x' = X / Z and y' = Y / Z when the camera focal length is not exactly 1. Furthermore, one cannot compute x' and y' for we don't know (X, Y, Z). (3) Unfortunately, things get even murkier when we refer to the writings in Intel's Open Source Computer Vision Library Reference Manual's section Lens Distortion (page 6-4), which states in part: "Let ( u, v ) be true pixel image coordinates, that is, coordinates with ideal projection, and ( u ~, v ~ ) be corresponding real observed (distorted) image coordinates. Similarly, ( x, y ) are ideal (distortion-free) and ( x ~, y ~ ) are real (distorted) image physical coordinates. Taking into account two expansion terms gives the following: x ~ = x * ( 1 + k1 * r^2 + k2 * r^4 ) + [ 2 p1 * x * y + p2 * ( r^2 + 2 * x^2 ) ] y ~ = y * ( 1 + k1 * r^2 + k2 * r^4 ] + [ 2 p2 * x * y + p2 * ( r^2 + 2 * y^2 ) ], where r = sqrt( x^2 + y^2 ). ... "Because u ~ = cx + fx * u and v ~ = cy + fy * v , … the resultant system can be rewritten as follows: u ~ = u + ( u – cx ) * [ k1 * r^2 + k2 * r^4 + 2 * p1 * y + p2 * ( r^2 / x + 2 * x ) ] v ~ = v + ( v – cy ) * [ k1 * r^2 + k2 * r^4 + 2 * p2 * x + p1 * ( r^2 / y + 2 * y ) ] The latter relations are used to undistort images from the camera." Well, it would appear that the expressions involving x ~ and y ~ coincided with the two expressions given at the top of this writing involving xcorrected and ycorrected. However, x ~ and y ~ do not refer to corrected coordinates, according to the given description. I don't understand the distinction between the meaning of the coordinates ( x ~, y ~ ) and ( u ~, v ~ ), or for that matter, between the pairs ( x, y ) and ( u, v ). From their descriptions it appears their only distinction is that ( x ~, y ~ ) and ( x, y ) refer to 'physical' coordinates while ( u ~, v ~ ) and ( u, v ) do not. What is this distinction all about? Aren't they all physical coordinates? I'm lost! Thanks for any input!

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• Is It Possible To Use Javascript/CSS To Swap Style Sheets When A Mobile Device Rotates?

  - by Sean M

  I am working on a site that must be designed with mobile accessibility in mind. As part of our brainstorming, we wondered whether it's possible to detect, for a mobile browser (i.e. Mobile Safari or the Android browser), when the viewing device has changed orientation, and to use that as a trigger to change page content? As the title of this question implies, our best-case scenario is the ability to detect the orientation change and use it to alter the CSS on the fly so as to present a slightly different page for landscape versus portrait. Of course we can just design for a page that looks good one way and make it obvious that it's supposed to be viewed that way, but the cool-stuff factor of a page that looks good either way is pretty appealing. Is this idea implementable? Practical?

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• CSG operations on implicit surfaces with marching cubes

  - by Mads Elvheim

  I render isosurfaces with marching cubes, (or perhaps marching squares as this is 2D) and I want to do set operations like set difference, intersection and union. I thought this was easy to implement, by simply choosing between two vertex scalars from two different implicit surfaces, but it is not. For my initial testing, I tried with two spheres, and the set operation difference. i.e A - B. One sphere is moving and the other one is stationary. Here's the approach I tried when picking vertex scalars and when classifying corner vertices as inside or outside. The code is written in C++. OpenGL is used for rendering, but that's not important. Normal rendering without any CSG operations does give the expected result. void march(const vec2& cmin, //min x and y for the grid cell const vec2& cmax, //max x and y for the grid cell std::vector<vec2>& tri, float iso, float (*cmp1)(const vec2&), //distance from stationary sphere float (*cmp2)(const vec2&) //distance from moving sphere ) { unsigned int squareindex = 0; float scalar[4]; vec2 verts[8]; /* initial setup of the grid cell */ verts[0] = vec2(cmax.x, cmax.y); verts[2] = vec2(cmin.x, cmax.y); verts[4] = vec2(cmin.x, cmin.y); verts[6] = vec2(cmax.x, cmin.y); float s1,s2; /********************************** ********For-loop of interest****** *******Set difference between **** *******two implicit surfaces****** **********************************/ for(int i=0,j=0; i<4; ++i, j+=2){ s1 = cmp1(verts[j]); s2 = cmp2(verts[j]); if((s1 < iso)){ //if inside sphere1 if((s2 < iso)){ //if inside sphere2 scalar[i] = s2; //then set the scalar to the moving sphere } else { scalar[i] = s1; //only inside sphere1 squareindex |= (1<<i); //mark as inside } } else { scalar[i] = s1; //inside neither sphere } } if(squareindex == 0) return; /* Usual interpolation between edge points to compute the new intersection points */ verts[1] = mix(iso, verts[0], verts[2], scalar[0], scalar[1]); verts[3] = mix(iso, verts[2], verts[4], scalar[1], scalar[2]); verts[5] = mix(iso, verts[4], verts[6], scalar[2], scalar[3]); verts[7] = mix(iso, verts[6], verts[0], scalar[3], scalar[0]); for(int i=0; i<10; ++i){ //10 = maxmimum 3 triangles, + one end token int index = triTable[squareindex][i]; //look up our indices for triangulation if(index == -1) break; tri.push_back(verts[index]); } } This gives me weird jaggies: It looks like the CSG operation is done without interpolation. It just "discards" the whole triangle. Do I need to interpolate in some other way, or combine the vertex scalar values? I'd love some help with this. A full testcase can be downloaded HERE

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• How to improve my LDAP schema?

  - by asmaier

  Hello, I have a OpenLDAP Database and it holds some project objects that look like dn: cn=Proj1,ou=Project,ou=ua,dc=org cn: Proj1 objectClass: top objectClass: posixGroup member: 001ag member: 002ag System: ABEL System: PCx Budget: ABEL:1000000:0.3 Budget: PCx:300000:0.3 One can see that the Budget attribute is a ":"-separated string, where the first part holds the name of the system the budget is for, the second part holds some budget (which may change every month) and the last entry is a conversion factor for the budget of that system. Seeing this, I thought this is bad database design, since attribute values should always be atomic. But how can I improve that in LDAP, so that I can do a direct ldapsearch or a direct ldapmodify of the budget of System "ABEL" instead of writing a script, that will have to parse and split the ":"-separated string?

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• Is there a HIPAA certification that would be helpful to programmers?

  - by Aequitarum Custos

  I work at a Medical Billing company that's software handles many facets of the centers practice, including patients, treatments, etc. To be frank, the only thing I know about HIPAA is security is paramount. I was wondering if there were any training courses with an earned certification proving knowledge/experience that I could use to increase my worth to the company, and give them a selling point (we have HIPAA certified employees). I did a Google search and found this site, but it does not appear legitimate, and I'm trying to avoid any of those fake certification/degree sites. Does anyone know of any recognized and legitimate (preferably government sponsored) HIPAA certifications useful to programmers? If state is a factor, I live in Oklahoma.

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• Calculating negative fractions in Objective C

  - by Mark Reid

  I've been coding my way through Steve Kochan's Programming in Objective-C 2.0 book. I'm up to an exercise in chapter 7, ex 4, in case anyone has the book. The question posed by the exercise it will the Fraction class written work with negative fractions such as -1/2 + -2/3? Here's the implementation code in question - @implementation Fraction @synthesize numerator, denominator; -(void) print { NSLog(@"%i/%i", numerator, denominator); } -(void) setTo: (int) n over: (int) d { numerator = n; denominator = d; } -(double) convertToNum { if (denominator != 0) return (double) numerator / denominator; else return 1.0; } -(Fraction *) add: (Fraction *) f { // To add two fractions: // a/b + c/d = ((a * d) + (b * c)) / (b * d) // result will store the result of the addition Fraction *result = [[Fraction alloc] init]; int resultNum, resultDenom; resultNum = (numerator * f.denominator) + (denominator * f.numerator); resultDenom = denominator * f.denominator; [result setTo: resultNum over: resultDenom]; [result reduce]; return result; } -(Fraction *) subtract: (Fraction *) f { // To subtract two fractions: // a/b - c/d = ((a * d) - (b * c)) / (b * d) // result will store the result of the addition Fraction *result = [[Fraction alloc] init]; int resultNum, resultDenom; resultNum = numerator * f.denominator - denominator * f.numerator; resultDenom = denominator * f.denominator; [result setTo: resultNum over: resultDenom]; [result reduce]; return result; } -(Fraction *) multiply: (Fraction *) f { // To multiply two fractions // a/b * c/d = (a*c) / (b*d) // result will store the result of the addition Fraction *result = [[Fraction alloc] init]; int resultNum, resultDenom; resultNum = numerator * f.numerator; resultDenom = denominator * f.denominator; [result setTo: resultNum over: resultDenom]; [result reduce]; return result; } -(Fraction *) divide: (Fraction *) f { // To divide two fractions // a/b / c/d = (a*d) / (b*c) // result will store the result of the addition Fraction *result = [[Fraction alloc] init]; int resultNum, resultDenom; resultNum = numerator * f.denominator; resultDenom = denominator * f.numerator; [result setTo: resultNum over: resultDenom]; [result reduce]; return result; } -(void) reduce { int u = numerator; int v = denominator; int temp; while (v != 0) { temp = u % v; u = v; v = temp; } numerator /= u; denominator /= u; } @end My question to you is will it work with negative fractions and can you explain how you know? Part of the issue is I don't know how to calculate negative fractions myself so I'm not too sure how to know. Many thanks.

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• Rails routing to XML/JSON without views gone mad

  - by John Schulze

  I have a mystifying problem. In a very simple Ruby app i have three classes: Drivers, Jobs and Vehicles. All three classes only consist of Id and Name. All three classes have the same #index and #show methods and only render in JSON or XML (this is in fact true for all their CRUD methods, they are identical in everything but name). There are no views. For example: def index @drivers= Driver.all respond_to do |format| format.js { render :json => @drivers} format.xml { render :xml => @drivers} end end def show @driver = Driver.find(params[:id]) respond_to do |format| format.js { render :json => @driver} format.xml { render :xml => @driver} end end The models are similarly minimalistic and only contain: class Driver< ActiveRecord::Base validates_presence_of :name end In routes.rb I have: map.resources :drivers map.resources :jobs map.resources :vehicles map.connect ':controller/:action/:id' map.connect ':controller/:action/:id.:format' I can perform POST/create, GET/index and PUT/update on all three classes and GET/read used to work as well until I installed the "has many polymorphs" ActiveRecord plugin and added to environment.rb: require File.join(File.dirname(__FILE__), 'boot') require 'has_many_polymorphs' require 'active_support' Now for two of the three classes I cannot do a read any more. If i go to localhost:3000/drivers they all list nicely in XML but if i go to localhost:3000/drivers/3 I get an error: Processing DriversController#show (for 127.0.0.1 at 2009-06-11 20:34:03) [GET] Parameters: {"id"=>"3"} [4;36;1mDriver Load (0.0ms)[0m [0;1mSELECT * FROM "drivers" WHERE ("drivers"."id" = 3) [0m ActionView::MissingTemplate (Missing template drivers/show.erb in view path app/views): app/controllers/drivers_controller.rb:14:in `show' ...etc This is followed a by another unexpected error: Processing ApplicationController#show (for 127.0.0.1 at 2009-06-11 21:35:52)[GET] Parameters: {"id"=>"3"} NameError (uninitialized constant ApplicationController::AreaAccessDenied): ...etc What is going on here? Why does the same code work for one class but not the other two? Why is it trying to do a #view on the ApplicationController? I found that if I create a simple HTML view for each of the three classes these work fine. To each class I add: format.html # show.html.erb With this in place, going to localhost:3000/drivers/3 renders out the item in HTML and I get no errors in the log. But if attach .xml to the URL it again fails for two of the classes (with the same error message as before) while one will output XML as expected. Even stranger, on the two failing classes, when adding .js to the URL (to trigger JSON rendering) I get the HTML output instead! Is it possible this has something to do with the "has many polymorphs" plugin? I have heard of people having routing issues after installing it. Removing "has many polymorphs" and "active support" from environment.rb (and rebooting the sever) seems to make no difference whatsoever. Yet my problems started after it was installed. I've spent a number of hours on this problem now and am starting to get a little desperate, Google turns up virtually no information which makes me suspect I must have missed something elementary. Any enlightenment or hint gratefully received! JS

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• Changing text size on a ggplot bump plot

  - by Tom Liptrot

  Hi, I'm fairly new to ggplot. I have made a bumpplot using code posted below. I got the code from someones blog - i've lost the link.... I want to be able to increase the size of the lables (here letters which care very small on the left and right of the plot) without affecting the width of the lines (this will only really make sense after you have run the code) I have tried changing the size paramater but that always alter the line width as well. Any suggestion appreciated. Tom require(ggplot2) df<-matrix(rnorm(520), 5, 10) #makes a random example colnames(df) <- letters[1:10] Price.Rank<-t(apply(df, 1, rank)) dfm<-melt(Price.Rank) names(dfm)<-c( "Date","Brand", "value") p <- ggplot(dfm, aes(factor(Date), value, group = Brand, colour = Brand, label = Brand)) p1 <- p + geom_line(aes(size=2.2, alpha=0.7)) + geom_text(data = subset(dfm, Date == 1), aes(x = Date , size =2.2, hjust = 1, vjust=0)) + geom_text(data = subset(dfm, Date == 5), aes(x = Date , size =2.2, hjust = 0, vjust=0))+ theme_bw() + opts(legend.position = "none", panel.border = theme_blank()) p1 + theme_bw() + opts(legend.position = "none", panel.border = theme_blank())

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• New to AVL tree implementation.

  - by nn

  I am writing a sliding window compression algorithm (LZ77) that searches for phrases in a "moving" dictionary. So far I have written a BST where each node is stored in an array and it's index in the array is also the value of the starting position in the window itself. I am now looking at transforming the BST to an AVL tree. I am a little confused at the sample implementations I have seen. Some only appear to store the balance factors whereas others store the height of each tree. Are there any performance advantage/disadvantages of storing the height and/or balance factor for each node? Apologies if this is a very simple question, but I'm still not visualizing how I want to restructure my BST to implement height balancing. Thanks.

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• How to prevent traffic to/from a slow Cassandra node using Python

  - by Sergio Ayestarán

  Intro: I have a Python application using a Cassandra 1.2.4 cluster with a replication factor of 3, all reads and writes are done with a consistency level of 2. To access the cluster I use the CQL library. The Cassandra cluster is running on rackspace's virtual servers. The problem: From time to time one of the nodes can become slower than usual, in this case I want to be able to detect this situation and prevent making requests to the slow node and if possible to stop using it at all (this should theoretically be possible since the RF is 3 and the CL is 2 for every single request). The questions: What's the best way of detecting the slow node from a Python application? Is there a way to stop using one of the Cassandra nodes from Python in this scenario without human intervention? Thanks in advance!

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• How to interpret trackpad pinch gestures to zoom IKImageBrowserView

  - by Fraser Speirs

  I have an IKImageBrowserView that I want to be able to pinch-zoom using a multi-touch trackpad on a recent Mac laptop. The Cocoa Event Handling Guide, in the section Handling Gesture Events says: The magnification accessor method returns a floating-point (CGFloat) value representing a factor of magnification ..and goes on to show code that adjusts the size of the view by multiplying height and width by magnification + 1.0. This doesn't seem to be the right approach for zooming IKImageBrowserView, whose zoomValue property is clamped between 0.0 and 1.0. So, does anyone know how to interpret the event in -[NSResponder magnifyWithEvent:] to zoom IKImageBrowserView?

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• Program contains 2 nested loops which contain 4 if conditionals. How many paths?

  - by Student4Life

  In Roger Pressman's book, there is an example described of a program with 2 nested loops, the inner loop enclosing four if statements. The two loops can execute up to 20 times. He states that this makes about 10^14 paths. To get a number this large, it seems the paths inside the loops are multipllied by 2^40, i.e. 2^20 times 2^20 to account for all the possibilities of going through the two loops. I can't see why this factor is not just 400, i.e. 20 times 20. Can someone shed some light? It will help if you have the ppt slides and can see the program graph. Thanks.

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• Keyboard for programming

  - by exhuma

  This may seem a bit a tangential topic. It's not directly related to actual code, but is important for our line of work nevertheless. Over the years, I've switched keyboards a few times. All of them had slightly different key layouts. And I'm not talking about the language/locale layout, but the physical layout! Why not the locale layout? Well, quite frankly, that's easy to change via software. I personally have a German keyboard but have it set to the UK layout. Why? It's quite hard to find different layouts in the shops where I live. Even ordering is not always easy in the shops. So that leaves me with Internet shops. But I prefer to "test" my keyboards before buying. The most notable changes are: Mangled "Home Key Block" I've seen this first on a Logitech keyboard, but it may have originated elsewhere. Shape of the "Enter" key I've seen three different cases so far: Two lines high, wider at the top Two lines high, wider at the bottom One line high Shape of the Backspace button I've seen two types so far: One "character" wide Two "characters" wide OS Keys For Macs, you have the Option and Command buttons, for Windows you have the Windows and Context Menu buttons. Cherry even produced a Linux keyboard once (unfortunately I cannot find many details except news results). I assume a dedicated Linux keyboard would sport a Compose key and had the SysRq always labelled as well (note that some standard layouts do this already). Obviously... .. all these differences entail that some keys have to be moved around the board a lot. Which means, if you are used to one and have to work on another one, you happen to hit the wrong keys quite often. As it happens, this is much more annoying for programmers as it is for people who write texts. Mainly because the keys which are moved around are special character keys, often used in programming. Often these hardware layouts depend also indirectly on where you buy the keyboards. Honestly, I haven't seen a keyboard with a one-line "Enter" key in Germany, nor Luxembourg. I may just have missed it but that's how it looks to me at least. A survey I've seen some attempts at surveys in the style "which keyboard is best for programming". But they all - in my opinion - are not using comparable sets. So I was wondering if it was possible to concoct a survey taking the above criteria into account. But ignoring key dimensions that one would be a bit overkill I guess ;) From what I can see there are the following types of physical layout: Backspace: 2-characters wide Enter: 2-Lines, wider top Backspace: 2-characters wide Enter: 1-Line Backspace: 1-character wide Enter: 2-Lines, wider bottom Then there are the other possible permutations (home-key block, os-keys), which in total makes for quite a large list of categories. Now, I wonder... Would anyone be interested in such a survey? I personally would. Because I am looking for the perfect fit for me. If yes, then I could really use the help of anyone here to propose some models to include in the survey. Once I have some models for each category (I'd say at least 3 per category) I could go ahead and write up a survey, put it on-line and let the it collect data for a while. What do you think?

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• using BOSH/similar technique for existing application/system

  - by SnapConfig.com

  We've an existing system which connects to the the back end via http (apache/ssl) and polls the server for new messages, needless to say we have scalability issues. I'm researching on removing this polling and have come across BOSH/XMPP but I'm not sure how we should take the BOSH technique (using long lived http connection). I've seen there are few libraries available but the entire thing seems bloaty since we do not need buddy lists etc and simply want to notify the clients of available messages. The client is written in C/C++ and works across most OS so that is an important factor. The server is in Java. does bosh result in huge number of httpd processes? since it has to keep all the clients connected, what would be the limit on that. we are also planning to move to 64 bit JVM/apache what would be the max limit of clients in that case. any hints?

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• Hidden UIView Orientation Change / Layout problems

  - by gargantaun

  The Problem: I have two View Controllers loaded into a root View Controller. Both sub view layouts respond to orientation changes. I switch between the two views using [UIView transformationFromView:...]. Both sub views work fine on their own, but if... Views are swapped Orientation Changes Views are swapped again the View that was previously hidden has serious layout problems. The more I repeat these steps the worse the problem gets. Implementation Details I have three viewsControllers. MyAppViewController A_ViewController B_ViewController A & B ViewControllers have a background image each, and a UIWebView and an AQGridView respectively. To give you an example of how i'm setting it all up, here's the loadView method for A_ViewController... - (void)loadView { [super loadView]; // background image // Should fill the screen and resize on orientation changes UIImageView *bg = [[UIImageView alloc] initWithFrame:self.view.bounds]; bg.contentMode = UIViewContentModeCenter; bg.autoresizingMask = UIViewAutoresizingFlexibleHeight | UIViewAutoresizingFlexibleWidth; bg.image = [UIImage imageNamed:@"fuzzyhalo.png"]; [self.view addSubview:bg]; // frame for webView // Should have a margin of 34 on all sides and resize on orientation changes CGRect webFrame = self.view.bounds; webFrame.origin.x = 34; webFrame.origin.y = 34; webFrame.size.width = webFrame.size.width - 68; webFrame.size.height = webFrame.size.height - 68; projectView = [[UIWebView alloc] initWithFrame:webFrame]; projectView.autoresizingMask = UIViewAutoresizingFlexibleHeight | UIViewAutoresizingFlexibleWidth; [self.view addSubview:projectView]; } For the sake of brevity, the AQGridView in B_ViewController is set up pretty much the same way. Now both these views work fine on their own. However, I use both of them in the AppViewController like this... - (void)loadView { [super loadView]; self.view.autoresizesSubviews = YES; [self setWantsFullScreenLayout:YES]; webView = [[WebProjectViewController alloc] init]; [self.view addSubview:webView.view]; mainMenu = [[GridViewController alloc] init]; [self.view addSubview:mainMenu.view]; activeView = mainMenu; [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(switchViews:) name:SWAPVIEWS object:nil]; } and I switch betweem the two views using my own switchView method like this - (void) switchViews:(NSNotification*)aNotification; { NSString *type = [aNotification object]; if ([type isEqualToString:MAINMENU]){ [UIView transitionFromView:activeView.view toView:mainMenu.view duration:0.75 options:UIViewAnimationOptionTransitionFlipFromRight completion:nil]; activeView = mainMenu; } if ([type isEqualToString:WEBVIEW]) { [UIView transitionFromView:activeView.view toView:webView.view duration:0.75 options:UIViewAnimationOptionTransitionFlipFromLeft completion:nil]; activeView = webView; } // These don't seem to do anything //[mainMenu.view setNeedsLayout]; //[webView.view setNeedsLayout]; } I'm fumbling my way through this, and I suspect a lot of what i've done is implemented incorrectly so please feel free to point out anything that should be done differently, I need the input. But my primary concern is to understand what's causing the layout problems. Here's two images which illustrate the nature of the layout issues... UPDATE: I just noticed that when the orientation is landscape, the transition flips vertically, when I would expect it to be horizontal. I don't know wether that's a clue as to what might be going wrong. Switch to the other view... change orientation.... switch back....

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• How to make JQGrid scroll properly in IE6?

  - by mcv

  I've got a JQGrid that needs to scroll. It works fine in Firefox, but in IE6, the grid stays stationary while the rest of the content scrolls underneath it. What might be a complicating factor is that the grid is inside tabs, inside a dialog. I've googled all over the place, but I can't find a solution for this problem, so I turn to Stackoverflow. Does anyone here know what could cause this behavior? I'm using jqgrid 3.5.3, should that matter.

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• B-Tree Revision

  - by stan

  Hi, If we are looking for line intersections (horizontal and vertical lines only) and we have n lines with half of them vertical and no intersections then Sorting the list of line end points on y value will take N log N using mergesort Each insert delete and search of our data structue (assuming its a b-tree) will be < log n so the total search time will be N log N What am i missing here, if the time to sort using mergesort takes a time of N log N and insert and delete takes a time of < log n are we dropping the constant factor to give an overal time of N log N. If not then how comes < log n goes missing in total ONotation run time? Thanks

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