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• How do you submit an authenticated HTML form using XUL (Firefox extension) Javascript?

  - by machineghost

  I am working on a Firefox extension, and in that extension I am trying to use AJAX to submit a form on a webpage. I am using: var request = Components.classes["@mozilla.org/xmlextras/xmlhttprequest;1"].createInstance(Components.interfaces.nsIXMLHttpRequest); request.onload = loadHandler; request.open("POST", url, true); request.send(values); to make the request, and it works ... mostly. The one problem is that the form has an authentication token on it, and I need to submit that token with my POST. I tried doing a GET separately to get this token, but by the time I made my second (POST) request my session had (evidently) changed, and the authenticity token was considered invalid. Does anyone know of a way to use the XUL/Chrome Javscript to maintain a constant session across multiple requests (all "behind the scenes") for something this? I'm still a XUL n00b, so there may be a totally obvious alternative that I'm missing (eg. hidden IFRAME; I tried that briefly but couldn't get it to work).

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• Is a control's OnInit called even when attaching it during parent's OnPreRender?

  - by Xerion

  My original understanding was that the asp.net page lifecycle is run once for all pages and controls under normal circumstances. When I attached a control during a container's OnPreRender, I encountered a situation where the control's OnInit was not called. OK, I considered that a bug in my code and fixed as such, by attaching the control earlier. But just today, I encountered a situation where OnInit for a control seems to be called after the normal OnInit has been done for everyone else. See stack below. It seems that during the page's PreRender, the control's OnInit is called as it is being dynamically added. So I just want to confirm exactly what ASP.NET's behavior is? Does it actually keep track of the stage of each control's lifecycle, and upon adding a new control, it will run from the very beginning? [HttpException (0x80004005): The control collection cannot be modified during DataBind, Init, Load, PreRender or Unload phases.] System.Web.UI.ControlCollection.Add(Control child) +8678663 MyCompany.Web.Controls.SetStartPageWrapper.Initialize() MyCompany.Web.Controls.SetStartPageWrapper.OnInit(EventArgs e) System.Web.UI.Control.InitRecursive(Control namingContainer) +333 System.Web.UI.Control.InitRecursive(Control namingContainer) +210 System.Web.UI.Control.AddedControl(Control control, Int32 index) +198 System.Web.UI.ControlCollection.Add(Control child) +80 MyCompany.Web.Controls.PageHeader.OnPreRender(EventArgs e) in System.Web.UI.Control.PreRenderRecursiveInternal() +80 System.Web.UI.Control.PreRenderRecursiveInternal() +171 System.Web.UI.Control.PreRenderRecursiveInternal() +171 System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +842

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• What library can I use to do simple, lightweight message passing?

  - by Mike

  I will be starting a project which requires communication between distributed nodes(the project is in C++). I need a lightweight message passing library to pass very simple messages(basically just strings of text) between nodes. The library must have the following characteristics: No external setup required. I need to be able to get everything up-and-running in my code - I don't want to require the user to install any packages or edit any configuration files(other than a list of IP addresses and ports to connect to). The underlying protocol which the library uses must be TCP(or if it is UDP, the library must guarantee the eventual receipt of the message). The library must be able to send and receive arbitrarily large strings(think up to 3GB+). The library needn't support any security mechanisms, fault tolerance, or encryption - I just need it to be fast, simple, and easy to use. I've considered MPI, but concluded it would require too much setup on the user's machine for my project. What library would you recommend for such a project? I would roll my own, but due to time constraints, I don't think that will be feasible.

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• Unit Testing the Use of TransactionScope

  - by Randolpho

  The preamble: I have designed a strongly interfaced and fully mockable data layer class that expects the business layer to create a TransactionScope when multiple calls should be included in a single transaction. The problem: I would like to unit test that my business layer makes use of a TransactionScope object when I expect it to. Unfortunately, the standard pattern for using TransactionScope is a follows: using(var scope = new TransactionScope()) { // transactional methods datalayer.InsertFoo(); datalayer.InsertBar(); scope.Complete(); } While this is a really great pattern in terms of usability for the programmer, testing that it's done seems... unpossible to me. I cannot detect that a transient object has been instantiated, let alone mock it to determine that a method was called on it. Yet my goal for coverage implies that I must. The Question: How can I go about building unit tests that ensure TransactionScope is used appropriately according to the standard pattern? Final Thoughts: I've considered a solution that would certainly provide the coverage I need, but have rejected it as overly complex and not conforming to the standard TransactionScope pattern. It involves adding a CreateTransactionScope method on my data layer object that returns an instance of TransactionScope. But because TransactionScope contains constructor logic and non-virtual methods and is therefore difficult if not impossible to mock, CreateTransactionScope would return an instance of DataLayerTransactionScope which would be a mockable facade into TransactionScope. While this might do the job it's complex and I would prefer to use the standard pattern. Is there a better way?

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• How to control virtual memory management in linux?

  - by chmike

  I'm writing a program that uses an mmap file to hold a huge buffer organized as an array of 64 MB blocks. The blocks are used to aggregate data received from different hosts through the network. As a consequence the total data size written in each block is not known in advance. Most of the time it is only 2MB but in some cases it can be up to 20MB or more. The data doesn't stay long in the buffer. 90% is deleted after less than a second and the rest is transmitted to another host. I would like to know if there is a way to tell the virtual memory manager that ram pages are not dirty anymore when data is deleted. Should I use mmap and munmap when a block is used and released to control the virtual memory ? What would be the overhead of doing this ? Also, some colleagues expressed concerns about the performance impact of allocating such a big mmap space. I expect it to behave like a swap file so that only dirty pages are to be considered.

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• persist values/variables from page to page

  - by Todd

  Hello, I'm wondering if there's another solution to my problem, that's considered more the Sharepoint way. FIrstly, my site is an Internet site, not Intranet. The problem is, all I'm trying to do is save values/variables from page to page in Sharepoint. I know the issue with Session Variables, but this seems to be the only way I can see to accomplish this. I know there are webparts that can store this value, but am I wrong in thinking this won't be persisted from page to page? Basically, I'll be extending the Content Query Web Part to dynamically filter it's results based off of a variable/value. The user chooses their 'area' from a dropdown, and the CQWP in the site will change and query results based off of this value (It will be a provincial structure as it is a Canadian site, so if someone chooses the province 'Ontario', this value is saved in a global variable, and these extended CQWP that are throughout the site, will get this value, and query lists flagged as Ontario). Is Session variables the only solution? Thanks everyone!

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• How to hold a queue of messages and have a group of working threads without polling?

  - by Mark

  I have a workflow that I want to looks something like this: / Worker 1 \ =Request Channel= - [Holding Queue|||] - Worker 2 - =Response Channel= \ Worker 3 / That is: Requests come in and they enter a FIFO queue Identical workers then pick up tasks from the queue At any given time any worker may work only one task When a worker is free and the holding queue is non-empty the worker should immediately pick up another task When tasks are complete, a worker places the result on the Response Channel I know there are QueueChannels in Spring Integration, but these channels require polling (which seems suboptimal). In particular, if a worker can be busy, I'd like the worker to be busy. Also, I've considered avoiding the queue altogether and simply letting tasks round-robin to all workers, but it's preferable to have a single waiting line as some tasks may be accomplished faster than others. Furthermore, I'd like insight into how many jobs are remaining (which I can get from the queue) and the ability to cancel all or particular jobs. How can I implement this message queuing/work distribution pattern while avoiding a polling? Edit: It appears I'm looking for the Message Dispatcher pattern -- how can I implement this using Spring/Spring Integration?

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• Exceptional C++[Bug]?

  - by gautam kumar

  I have been reading Exceptional C++ by Herb Sutter. On reaching Item 32 I found the following namespace A { struct X; struct Y; void f( int ); void g( X ); } namespace B { void f( int i ) { f( i ); // which f()? } } This f() calls itself, with infinite recursion. The reason is that the only visible f() is B::f() itself. There is another function with signature f(int), namely the one in namespace A. If B had written "using namespace A;" or "using A::f;", then A::f(int) would have been visible as a candidate when looking up f(int), and the f(i) call would have been ambiguous between A::f(int) and B::f(int). Since B did not bring A::f(int) into scope, however, only B::f(int) can be considered, so the call unambiguously resolves to B::f(int). But when I did the following.. namespace A { struct X; struct Y; void f( int ); void g( X ); } namespace B { using namespace A; void f( int i ) { f( i ); // No error, why? } } That means Herb Sutter has got it all wrong? If not why dont I get an error?

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• In SQL Server what is most efficient way to compare records to other records for duplicates with in

  - by Glenn

  We have an SQL Server that gets daily imports of data files from clients. This data is interrelated and we are always scrubbing it and having to look for suspect duplicate records between these files. Finding and tagging suspect records can get pretty complicated. We use logic that requires some field values to be the same, allows some field values to differ, and allows a range to be specified for how different certain field values can be. The only way we've found to do it is by using a cursor based process, and it places a heavy burden on the database. So I wanted to ask if there's a more efficient way to do this. I've heard it said that there's almost always a more efficient way to replace cursors with clever JOINS. But I have to admit I'm having a lot of trouble with this one. For a concrete example suppose we have 1 table, an "orders" table, with the following 6 fields. order_id, customer_id product_id, quantity, sale_date, price We want to look through the records to find suspect duplicates on the following example criteria. These get increasingly harder. 1. Records that have the same product_id, sale_date, and quantity but different customer_id's should be marked as suspect duplicates for review. 2. Records that have the same customer_id, product_id, quantity and have sale_dates within five days of each other should be marked as suspect duplicates for review 3. Records that have the same customer_id, product_id, but different quantities within 20 units, and sales dates within five days of each other should be considered suspect. Is it possible to satisfy each one of these criteria with a single SQL Query that uses JOINS? Is this the most efficient way to do this?

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• Prolog singleton variables in Python

  - by Rubens

  I'm working on a little set of scripts in python, and I came to this: line = "a b c d e f g" a, b, c, d, e, f, g = line.split() I'm quite aware of the fact that these are decisions taken during implementation, but shouldn't (or does) python offer something like: _, _, var_needed, _, _, another_var_needed, _ = line.split() as well as Prolog does offer, in order to exclude the famous singleton variables. I'm not sure, but wouldn't it avoid unnecessary allocation? Or creating references to the result of the split call does not count up as overhead? EDIT: Sorry, my point here is: in Prolog, as far as I'm concerned, in an expression like: test(L, N) :- test(L, 0, N). test([], N, N). test([_|T], M, N) :- V is M + 1, test(T, V, N). The variable represented by _ is not accessible, for what I suppose the reference to the value that does exist in the list [_|T] is not even created. But, in Python, if I use _, I can use the last value assigned to _, and also, I do suppose the assignment occurs for each of the variables _ -- which may be considered an overhead. My question here is if shouldn't there be (or if there is) a syntax to avoid such unnecessary attributions.

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• How can I abstract out the core functionality of several Rails applications?

  - by hornairs

  I'd like to develop a number of non-trivial Rails applications which all implement a core set of functionality but each have certain particular customizations, extensions, and aesthetic differences. How can I pull the core functionality (models, controllers, helpers, support classes, tests) common to all these systems out in such a way that updating the core will benefit every application based upon it? I've seen Rails Engines but they seem to be too detached, almost too abstracted to be built upon. I can seem them being useful for adding one component to an existing app, for example bolting on a blog engine to your existing e-commerce site. Since engines seem to be mostly self contained, it seems difficult and inconvenient to override their functionality and views while keeping DRY. I've also considered abstracting the code into a gem, but this seems a little odd. Do I make the gem depend on the Rails gems, and the define models & controllers inside it, and then subclass them in my various applications? Or do I define many modules inside the gem that I include in the different spots inside my various applications? How do I test the gem and then test the set of customizations and overridden functionality on top of it? I'm also concerned with how I'll develop the gem and the Rails apps in tandem, can I vendor a git repository of the gem into the app and push from that so I don't have to build a new gem every iteration? Also, are there private gem hosts/can I set my own gem source up? Also, any general suggestions for this kind of undertaking? Abstraction paradigms to adhere to? Required reading? Comments from the wise who have done this before? Thanks!

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• algorithm to generate maximum number of character 'A' using keystrokes 'A', CTRL + 'A', CTRL + 'C' and CTRL + 'V'

  - by munda

  This is an interview question from google. I am not able to solve it by myself. Can somebody throw some light? The question goes like this. Write a program to print the sequence of keystrokes such that it generates the maximum number of character 'A's. You are allowed to use only 4 keys: 'A', CTRL + 'A', CTRL + 'C' and CTRL + 'V'. Only N keystrokes are allowed. All CTRL+ characters are considered as one keystroke, so CTRL+A is one keystroke. e.g.: A, ctrl+A, ctrl+C, ctrl+V generates two As in 4 keystrokes. Edit: CTRL + A is Select All CTRL + C is copy CTRL + V is paste I did some mathematics. For any N, using x numbers of A's , one CTRL+A, one CTRL+C and y CTRL+V, we can generate max ((N-1)/2)^2 numbers of A's. But for some N M, it is better to use as many ^A, ^C and ^V as it doubles the number of As. Edit 2: ^A, ^V and ^C will not overwrite on the existing selection but it will append the copied selection to selected one.

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• What OpenGL functions are not GPU accelerated?

  - by Xavier Ho

  I was shocked when I read this (from the OpenGL wiki): glTranslate, glRotate, glScale Are these hardware accelerated? No, there are no known GPUs that execute this. The driver computes the matrix on the CPU and uploads it to the GPU. All the other matrix operations are done on the CPU as well : glPushMatrix, glPopMatrix, glLoadIdentity, glFrustum, glOrtho. This is the reason why these functions are considered deprecated in GL 3.0. You should have your own math library, build your own matrix, upload your matrix to the shader. For a very, very long time I thought most of the OpenGL functions use the GPU to do computation. I'm not sure if this is a common misconception, but after a while of thinking, this makes sense. Old OpenGL functions (2.x and older) are really not suitable for real-world applications, due to too many state switches. This makes me realise that, possibly, many OpenGL functions do not use the GPU at all. So, the question is: Which OpenGL function calls don't use the GPU? I believe knowing the answer to the above question would help me become a better programmer with OpenGL. Please do share some of your insights.

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• C# "Rename" Property in Derived Class

  - by Eric

  When you read this you'll be awfully tempted to give advice like "this is a bad idea for the following reason..." Bear with me. I know there are other ways to approach this. This question should be considered trivia. Lets say you have a class "Transaction" that has properties common to all transactions such as Invoice, Purchase Order, and Sales Receipt. Let's take the simple example of Transaction "Amount", which is the most important monetary amount for a given transaction. public class Transaction { public double Amount { get; set; } public TxnTypeEnum TransactionType { get; set; } } This Amount may have a more specific name in a derived type... at least in the real world. For example, the following values are all actually the same thing: Transaction - Amount Invoice - Subtotal PurchaseOrder - Total Sales Receipt - Amount So now I want a derived class "Invoice" that has a Subtotal rather than the generically-named Amount. Ideally both of the following would be true: In an instance of Transaction, the Amount property would be visible. In an instance of Invoice, the Amount property would be hidden, but the Subtotal property would refer to it internally. Invoice looks like this: public class Invoice : Transaction { new private double? Amount { get { return base.Amount; } set { base.Amount = value; } } // This property should hide the generic property "Amount" on Transaction public double? SubTotal { get { return Amount; } set { Amount = value; } } public double RemainingBalance { get; set; } } But of course Transaction.Amount is still visible on any instance of Invoice. Thanks for taking a look!

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• Do I need to Salt and Hash a randomly generated token?

  - by wag2639

  I'm using Adam Griffiths's Authentication Library for CodeIgniter and I'm tweaking the usermodel. I came across a generate function that he uses to generate tokens. His preferred approach is to reference a value from random.org but I considered that superfluous. I'm using his fall back approach of randomly generating a 20 character long string: $length = 20; $characters = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ'; $token = ''; for ($i = 0; $i < $length; $i++) { $token .= $characters[mt_rand(0, strlen($characters)-1)]; } He then hashes this token using a salt (I'm combing code from different functions) sha1($this->CI->config->item('encryption_key').$str); I was wondering if theres any reason to to run the token through the salted hash? I've read that simply randomly generating strings was a naive way of making random passwords but is the sh1 hash and salt necessary? Note: I got my encryption_key from https://www.grc.com/passwords.htm (63 random alpha-numeric)

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• Selectively search and replace certain lines using a regular expression

  - by eneveu

  I have a file containing a lot of SQL statements, such as: CREATE TABLE "USER" ( "ID" INTEGER PRIMARY KEY, "NAME" CHARACTER VARYING(50) NOT NULL, "AGE" INTEGER NOT NULL ); COPY "USER" (id, name, age) FROM stdin; 1 Skywalker 19 2 Kenobi 57 I want the column names in the COPY statements to be uppercased and quoted: COPY "USER" ("ID", "NAME", "AGE") FROM stdin; Using sed, I found the following regexp: sed -r 's/([( ])(\w+)([,)])/\1"\U\2\E"\3/g' It does replace the column names, but it is not selective enough, and replaces other words in the file: ~/test]$sed -r 's/([( ])(\w+)([,)])/\1"\U\2\E"\3/g' star_wars_example CREATE TABLE "USER" ( "ID" INTEGER PRIMARY "KEY", "NAME" CHARACTER VARYING("50")NOT "NULL", "AGE" INTEGER NOT NULL ); COPY "USER" ("ID", "NAME", "AGE") FROM stdin; 1 Skywalker 19 2 Kenobi 57 To avoid this problem, I want sed to only apply my regexp to the lines starting with COPY and ending with FROM stdin;. I have looked into lookahead / lookbehind, but they are not supported in sed. They seem to be supported in super-sed, but I am currently using Cygwin (Windows is mandatory here...) and it does not seem available in the package list. Is there a way to force sed to only consider specific line? I've considered piping my file through grep before applying sed, but other lines will then disappear from the output. Am I missing something obvious? It would be great if the answer was easily applicable on a default Cygwin install. I guess I could try installing super-sed on cygwin, but I'd like to know if there are more obvious ideas

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• Drools - Doing Complex Stuff inside a Rule Condition or Consequence

  - by mfcabrera

  Hello, In my company we are planning to use Drools a BRE for couple of projects. Now we trying to define some best-practices. My question is what should be and shouldn't be done inside a Rule Condition/Consequence. Given that we can write Java directly or call methods (for example From a Global object in the Working Memory). Example. Given a Rule that evaluates a generic Object (e.g. Person) have property set to true. Now, that specific propertie can only be defined for that Object going to the database and fetching that info. So we have two ways of implementing that: Alternative A: Go to the database and fetch the object property (true/false, a code) Insert the Object in the working memory Evaluate the rule Alternative B: Insert a Global Object that has a method that connects to the database and check for the property for the given object. Insert the Object to eval in Working Memory In the rule, call the Global Object and perform the access to the database Which of those is considered better? I really like A, but sometimes B is more straightforward, however what would happen if something like a Exception from the Database is raised? I have seen the alternative B implemented in the Drools 5.0 Book from Packt Publishing,however they are doing a mocking and they don't talk about the actual implications of going to the database at all. Thank you,

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• Concurrency problem with arrays (Java)

  - by Johannes

  For an algorithm I'm working on I tried to develop a blacklisting mechanism that can blacklist arrays in a specific way: If "1, 2, 3" is blacklisted "1, 2, 3, 4, 5" is also considered blacklisted. I'm quite happy with the solution I've come up with so far. But there seem to be some serious problems when I access a blacklist from multiple threads. The method "contains" (see code below) sometimes returns true, even if an array is not blacklisted. This problem does not occur if I only use one thread, so it most likely is a concurrency problem. I've tried adding some synchronization, but it didn't change anything. I also tried some slightly different implementations using java.util.concurrent classes. Any ideas on how to fix this? public class Blacklist { private static final int ARRAY_GROWTH = 10; private final Node root = new Node(); private static class Node{ private volatile Node[] childNodes = new Node[ARRAY_GROWTH]; private volatile boolean blacklisted = false; public void blacklist(){ this.blacklisted = true; this.childNodes = null; } } public void add(final int[] array){ synchronized (root) { Node currentNode = this.root; for(final int edge : array){ if(currentNode.blacklisted) return; else if(currentNode.childNodes.length <= edge) { currentNode.childNodes = Arrays.copyOf(currentNode.childNodes, edge + ARRAY_GROWTH); } if(currentNode.childNodes[edge] == null) { currentNode.childNodes[edge] = new Node(); } currentNode = currentNode.childNodes[edge]; } currentNode.blacklist(); } } public boolean contains(final int[] array){ synchronized (root) { Node currentNode = this.root; for(final int edge : array){ if(currentNode.blacklisted) return true; else if(currentNode.childNodes.length <= edge || currentNode.childNodes[edge] == null) return false; currentNode = currentNode.childNodes[edge]; } return currentNode.blacklisted; } } }

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• Code Analysis Warning CA1004 with generic method

  - by Vaccano

  I have the following generic method: // Load an object from the disk public static T DeserializeObject<T>(String filename) where T : class { XmlSerializer xmlSerializer = new XmlSerializer(typeof(T)); try { TextReader textReader = new StreamReader(filename); var result = (T)xmlSerializer.Deserialize(textReader); textReader.Close(); return result; } catch (FileNotFoundException) { } return null; } When I compile I get the following warning: CA1004 : Microsoft.Design : Consider a design where 'MiscHelpers.DeserializeObject(string)' doesn't require explicit type parameter 'T' in any call to it. I have considered this and I don't know a way to do what it requests with out limiting the types that can be deserialized. I freely admit that I might be missing an easy way to fix this. But if I am not, then is my only recourse to suppress this warning? I have a clean project with no warnings or messages. I would like to keep it that way. I guess I am asking "why this is a warning?" At best this seems like it should be a message. And even that seems a bit much. Either it can or it can't be fixed. If it can't then you are just stuck with the warning with no recourse but suppressing it. Am I wrong?

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• Compact data structure for storing a large set of integral values

  - by Odrade

  I'm working on an application that needs to pass around large sets of Int32 values. The sets are expected to contain ~1,000,000-50,000,000 items, where each item is a database key in the range 0-50,000,000. I expect distribution of ids in any given set to be effectively random over this range. The operations I need on the set are dirt simple: Add a new value Iterate over all of the values. There is a serious concern about the memory usage of these sets, so I'm looking for a data structure that can store the ids more efficiently than a simple List<int>or HashSet<int>. I've looked at BitArray, but that can be wasteful depending on how sparse the ids are. I've also considered a bitwise trie, but I'm unsure how to calculate the space efficiency of that solution for the expected data. A Bloom Filter would be great, if only I could tolerate the false negatives. I would appreciate any suggestions of data structures suitable for this purpose. I'm interested in both out-of-the-box and custom solutions. EDIT: To answer your questions: No, the items don't need to be sorted By "pass around" I mean both pass between methods and serialize and send over the wire. I clearly should have mentioned this. There could be a decent number of these sets in memory at once (~100).

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• Parsing: How to make error recovery in grammars like " a* b*"?

  - by Lavir the Whiolet

  Let we have a grammar like this: Program ::= a* b* where "*" is considered to be greedy. I usually implement "*" operator naively: Try to apply the expression under "*" to input one more time. If it has been applied successfully then we are still under current "*"-expression; try to apply the expression under "*" one more time. Otherwise we have reached next grammar expression; put characters parsed by expression under "*" back into input and proceed with next expression. But if there are errors in input in any of "a*" or "b*" part such a parser will "think" that in position of error both "a*" and "b*" have finished ("let's try "a"... Fail! OK, it looks like we have to proceed to "b*". Let's try "b"... Fail! OK, it looks like the string should have been finished...). For example, for string "daaaabbbbbbc" it will "say": "The string must end at position 1, delete superflous characters: daaaabbbbbbc". In short, greedy "*" operator becomes lazy if there are errors in input. How to make "*" operator to recover from errors nicely?

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• Dictionaries with more than one key per value in Python

  - by nickname

  I am attempting to create a nice interface to access a data set where each value has several possible keys. For example, suppose that I have both a number and a name for each value in the data set. I want to be able to access each value using either the number OR the name. I have considered several possible implementations: Using two separate dictionaries, one for the data values organized by number, and one for the data values organized by name. Simply assigning two keys to the same value in a dictionary. Creating dictionaries mapping each name to the corresponding number, and vice versa Attempting to create a hash function that maps each name to a number, etc. (related to the above) Creating an object to encapsulate all three pieces of data, then using one key to map dictionary keys to the objects and simply searching the dictionary to map the other key to the object. None of these seem ideal. The first seems ugly and unmaintainable. The second also seems fragile. The third/fourth seem plausible, but seem to require either much manual specification or an overly complex implementation. Finally, the fifth loses constant-time performance for one of the lookups. In C/C++, I believe that I would use pointers to reference the same piece of data from different keys. I know that the problem is rather similar to a database lookup problem by a non-key column, however, I would like (if possible), to maintain the approximate O(1) performance of Python dictionaries. What is the most Pythonic way to achieve this data structure?

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• emacs: How to intelligently handle buffer-modified when setting text properties?

  - by Cheeso

  The documentation on Text Properties says: Since text properties are considered part of the contents of the buffer (or string), and can affect how a buffer looks on the screen, any change in buffer text properties marks the buffer as modified. First, I don't understand that policy. Can anyone explain? The text props are not actually saved in the file, when the buffer is saved. So why mark the buffer as modified? For me, buffer-modified indicates "some changes have not yet been saved." but understanding the policy is just for my own amusement. More importantly, is there an already-established way that, in code, I can change syntax text properties on the text in a buffer, while keeping the buffer-modified flag set to whatever it was, prior to those changes? I'm thinking of something like save-excursion. It would be pretty easy to write, but this seems like a common case and I'd like to use the standard function, if possible. For more on the scenario - I have a mode that does a full text scan and sets syntax-tabe properties on the text. After opening a buffer, the scan runs, but it results in a buffer with buffer-modified set to t . As always, thanks.

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• Wrong values reported by pyPDF for various box regions

  - by romor

  Using pyPdf, for most files I get matched results concerning various box's dimensions compared to what Acrobat reports. However for some files I get different values reported by pyPdf and Acrobat, like: pyPdf: artBox: 595.3 x 841.9 bleedBox: 595.3 x 841.9 cropBox: 595.3 x 841.9 trimBox: 517.3 x 754 Acrobat: artBox: 439.35 x 666.13 pt bleedBox: 439.35 x 666.13 pt cropBox: 439.35 x 666.13 pt trimBox: 439.35 x 666.13 pt I thought it's units issue, but then ratio between widths and heights doesn't match also, not mentioning trimBox mismatch Correct results are those reported by Acrobat of course. Does someone know why is this and is there a way I get correct dimensions by using pyPdf? Thanks couple of minutes later... After reading this question: Are PDF box coordinates relative or absolute? I figured I didn't considered uper left corner to be different then 0 (zero). It turned out that box starts at 77.95 x 87.87, so if we reduce reported values of trimBox by this values correct result is obtained. artBox: 0 x 0 bleedBox: 0 x 0 cropBox: 0 x 0 trimBox: 77.95 x 87.87 Other boxes seem with misleading values or I misinterpret them. Snippet: from pyPdf import PdfFileReader pdfread = PdfFileReader(file('my.pdf', 'rb')) page = 1 width = pdfread.getPage(page).trimBox[2]-pdfread.getPage(page).trimBox[0] height = pdfread.getPage(page).trimBox[3] - pdfread.getPage(page).trimBox[1] print width, height

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• Body Mass Index program in haskell

  - by user364996

  Hi there. I'm trying to write a simple program in Haskell that can determine someone's body mass index. Here's what I have written: type Height = Float type Weight = Float type PeopleStats = [(String, Height, Weight)] and... bmi :: Height -> Weight -> Float bmi heightCm weightKg = weightKg/(heightCm)^2 healthy :: Height -> Weight -> Bool healthy heightCm weightKg | 25 > index && 18 < index = True | otherwise = False where index = bmi heightCm weightKg So far, the function "healthy" can calculate someone's BMI, and the function "healthyPeople" returns a boolean statement determining if the person's BMI falls within the limits which is considered normal for a healthy person. I want to write a function called "healthyPeople". healthyPeople :: PeopleStats -> [String] This function needs to take a list of PeopleStats and returns a list of names (Strings) of people who are deemed to be "healthy" from the "healthy" function. For example: If I input [("Lee", 65, 185), ("Wang", 170, 100), ("Tsu", 160, 120)] I will get a list of the names of the people whose BMI returns true form the boolean function in "healthy". Please help !!!!

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