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  • Generating Fibonacci series in F#

    - by photo_tom
    I'm just starting to learn F# using VS2010 and below is my first attempt at generating the Fibonacci series. What I'm trying to do is to build a list of all numbers less than 400. let fabList = let l = [1;2;] let mutable a = 1 let mutable b = 2 while l.Tail < 400 do let c = a + b l.Add(c) let a = b let b = c My first problem is that on the last statement, I'm getting an error message "Incomplete structured construct at or before this point in expression" on the last line. I don't understand what I'm doing wrong here. While this seems to be an obvious way to build the list in a fairly efficient way (from a c++/C# programmer), from what little I know of f#, this doesn't seem to feel to be the right way to do the program. Am I correct in this feeling?

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  • How to save an order (permutation) in an sql db

    - by Bendlas
    I have a tree structure in an sql table like so: CREATE TABLE containers ( container_id serial NOT NULL PRIMARY KEY, parent integer REFERENCES containers (container_id)) Now i want to define an ordering between nodes with the same parent. I Have thought of adding a node_index column, to ORDER BY, but that seem suboptimal, since that involves modifying the index of a lot of nodes when modifying the stucture. That could include adding, removing, reordering or moving nodes from some subtree to another. Is there a sql datatype for an ordered sequence, or an efficient way to emulate one? Doesn't need to be fully standard sql, I just need a solution for mssql and hopefully postgresql EDIT To make it clear, the ordering is arbitrary. Actually, the user will be able to drag'n'drop tree nodes in the GUI

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  • simple search in rails

    - by Adnan
    Hi, I'm making a simple search form in rails. In my search view I have two select boxes with fixed values like: SELECT BOX 1 SELECT BOX 2 ALL, ALL, FR, FR, US, US, DE DE And I have 2 fields in my DB with country_from and country_to. So for making a simple search like from FR to US I use: @search_result = Load.find(:all, :conditions => "country_from='#{params[:country_from]}' AND country_to='#{params[:country_to]}'" ) that is fine, but I need to implement the ALL option as well, so when I make a search like from DE to ALL I get a list with all countries in country_to I image I can do it with ifs...but what would be the most efficient way to do it?

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  • How can an SQL query return data from multiple tables

    - by Fluffeh
    I would like to know how to get data from multiple tables in my database, what types of methods are there to do this, what are joins and unions and how are they different from one another? When should I use each one compared to the others? I am planning to use this in my (for example - PHP) application, but don't want to run multiple queries against the database, what options do I have to get data from multiple tables in a single query? Note: I am writing this as I would like to be able to link to a well written guide on the numerous questions that I constantly come across in the PHP queue, so I can link to this for further detail when I post an answer. The answers cover off the following: Part 1 - Joins and Unions Part 2 - Subqueries Part 3 - Tricks and Efficient Code

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  • MySQL "IS IN" equivalent?

    - by nute
    A while ago I worked on a MS-SQL project and I remember a "IS IN" thing. I tried it on a MySQL project and it did not work. Is there an equivalent? Workaround? Here is the full query I am trying to run: SELECT * FROM product_product, product_viewhistory, product_xref WHERE ( (product_viewhistory.productId = product_xref.product_id_1 AND product_xref.product_id_2 = product_product.id) OR (product_viewhistory.productId = product_xref.product_id_2 AND product_xref.product_id_1 = product_product.id) ) AND product_product.id IS IN (SELECT DISTINCT pvh.productId FROM product_viewhistory AS pvh WHERE pvh.cookieId = :cookieId ORDER BY pvh.viewTime DESC LIMIT 10) AND product_viewhistory.cookieId = :cookieId AND product_product.outofstock='N' ORDER BY product_xref.hits DESC LIMIT 10 It's pretty big ... but the part I am interested in is: AND product_product.id IS IN (SELECT DISTINCT pvh.productId FROM product_viewhistory AS pvh WHERE pvh.cookieId = :cookieId ORDER BY pvh.viewTime DESC LIMIT 10) Which basically says I want the products to be in the "top 10" of that sub-query. How would you achieve that with MySQL (while trying to be efficient)?

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  • Prevent RegEx Hang on Large Matches...

    - by developerjay
    This is a great regular expression for dates... However it hangs indefinitely on this one page I tried... I wanted to try this page ( http://pleac.sourceforge.net/pleac%5Fpython/datesandtimes.html ) for the fact that it does have lots of dates on it and I want to grab all of them. I don't understand why it is hanging when it doesn't on other pages... Why is my regexp hanging and/or how could I clean it up to make it better/efficient ? Python Code: monthnames = "(?:Jan\w*|Feb\w*|Mar\w*|Apr\w*|May|Jun\w?|Jul\w?|Aug\w*|Sep\w*|Oct\w*|Nov(?:ember)?|Dec\w*)" pattern1 = re.compile(r"(\d{1,4}[\/\\\-]+\d{1,2}[\/\\\-]+\d{2,4})") pattern4 = re.compile(r"(?:[\d]*[\,\.\ \-]+)*%s(?:[\,\.\ \-]+[\d]+[stndrh]*)+[:\d]*[\ ]?(PM)?(AM)?([\ \-\+\d]{4,7}|[UTCESTGMT\ ]{2,4})*"%monthnames, re.I) patterns = [pattern4, pattern1] for pattern in patterns: print re.findall(pattern, s) btw... when i say im trying it against this site.. I'm trying it against the webpage source.

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  • Correct way to take absolute value of INT_MIN

    - by aka.nice
    I want to perform some arithmetic in unsigned, and need to take absolute value of negative int, something like do_some_arithmetic_in_unsigned_mode(int some_signed_value) { unsigned int magnitude; int negative; if(some_signed_value<0) { magnitude = 0 - some_signed_value; negative = 1; } else { magnitude = some_signed_value; negative = 0; } ...snip... } But INT_MIN might be problematic, 0 - INT_MIN is UB if performed in signed arithmetic. What is a standard/robust/safe/efficient way to do this in C?

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  • Retrieving a single Guid in CRM 4.0

    - by user1746560
    I'm new to CRM (version 4.0) and i'm trying to return a 'yearid' guide based on a given year (which is also stored in the entity).So far i've got: public static Guid GetYearID(string yearName) { ICrmService service = CrmServiceFactory.GetCrmService(); // Create the query object. QueryExpression query = new QueryExpression("year"); ColumnSet columns = new ColumnSet(); columns.AddColumn("yearid"); query.ColumnSet = columns; FilterExpression filter = new FilterExpression(); filter.FilterOperator = LogicalOperator.And; filter.AddCondition(new ConditionExpression { AttributeName = "yearName", Operator = ConditionOperator.Equal, Values = new object[] { yearName} }); query.Criteria = filter; } But my questions are: A) What code do in addition to this to actually store the Guid? B) Is using a QueryExpression the most efficient way to do this?

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  • Why the streams in C++?

    - by oh boy
    As you all know there are libraries using streams such as iostream and fstream. My question is: Why streams? Why didn't they stick with functions similar to print, fgets and so on (for example)? They require their own operators << and >> but all they do could be implemented in simple functions like above, also the function printf("Hello World!"); is a lot more readable and logical to me than cout << "Hello World"; I also think that all of those string abstractions in C++ all compile down to (less efficient) standard function calls in binary.

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  • Updating a database periodically with Java

    - by MSR
    I would like to perform updates to a MySQL database using two separate classes (that do different things) -- one doing so every 10 seconds, and the second every minute. I have a few gaps in my Java knowledge and I'm wondering what the best way to achieve it is. Importantly, if connectivity to the database is lost, I need reconnection attempts to occur indefinitely, and I'm guessing the use of Prepared Statements will make queries more efficient. Should the connection to the database be left open all the time or closed between the updates being run? Maybe I also need to think about clearing objects/resources out of memory if the class instances are going to be run indefinitely.

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  • How to correctly migrate urls from custom asp.net solution to Wordpress?

    - by Marek
    I have a web site built using asp.net with ugly URLs like /DisplayContent.aspx?id=789564. I know how to migrate the database, but the Wordpress urls will be (naturally) different. Can I simply write some mapping or do I have to include a rewrite rule for each subpage (300 pages) in .htaccess? Should I provide a rewrite rule for each existing page that would transform a full old url to the known new url, like for example: /DisplayContent.aspx?id=789798 -> /2010-5-10/Title-Of-The-Post Even if I manage to migrate the URLs, the structure of the HTML for the new content will naturally be different. How does this affect SEO? Should I run asp.net and wordpress side by side and issue the redirects from the asp.net application? What is the most efficient solution to this kind of migration of URLs without doing PHP programming?

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  • Hyperlinks in VS2008 Test Result Details

    - by Red XIII
    In case when resulting string in "Test Result Details" (TRD) is very long, the Visual Studio 2008 crashes. I fixed this by sending the result data into a file. There is a problem, however, because there isn't a simple way to open such file. Of course, I can manually open folder and then the file, but it isn't very efficient. Now, to the questions part. Is there a possibility to include in the "Error Message" part of TRD a hyperlink to a file? (something similar to what we can already find in the stack trace part) If not, is there any way to add such functionality (easy opening of a file) to TRD? If not, are there any ways to expand the default reporting of VS? Thanks for any help.

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  • Awk or Sed: File Annotation

    - by lukmac
    Hallo, my SO friend, my question is: Specification: annotate the fields of FILE_2 to the corresponding position of FILE_1. A field is marked, and hence identified, by a delimiter pair. I did this job in python before I knew awk and sed, with a couple hundred lines of code. Now I want to see how powerful and efficient awk and sed can be. Show me some masterpiece of awk or sed, please! The delimiter pairs can be configured in FILE_3, but let's assume the first delimiter in a pair is 'Marker (number i) start', the other one is 'Marker (number i) done' Example: |-----------------FILE_1------------------| text text text text blabla Marker_1_start Marker_1_done any text in between blabla Marker_2_start Marker_2_done text text |-----------------FILE_2------------------| Marker_1_start 11 1111 Marker_1_done Marker_2_start 2222 22 Marker_2_done Expected Output: |-----------------FILE_Out------------------| text text text text blabla Marker_1_start 11 1111 Marker_1_done any text in between blabla Marker_2_start 2222 22 Marker_2_done text text

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  • Ruby on Rails: Best way to save search queries in a database

    - by Adam Templeton
    For a RoR app I'm helping develop, I need to save all search queries in a database so I can analyze them later. My plan right now is to create a Result model and table, and just save each search query's text in that table, along with a user's ID, the time, etc. However, the app has about 15,000 users, so I'm afraid the single table approach won't be super efficient when it comes time to parse that data. (The database is setup via MySQL, if that factors in at all.) Am I just being paranoid? Is there a Ruby gem that handles this sort of thing, or a better approach I could take? Any input would be appreciated.

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  • Convert unusual string into date time

    - by BlueChippy
    I have a system that outputs dates in the format "1{yy}{MM}{dd}" and I am trying to find a good way to parse it back into a real date. At the moment I am using this: var value = "1110825"; var z = Enumerable.Range(1,3).Select(i => int.Parse(value.Substring(i, 2))).ToList(); var d = new DateTime(2000 + z[0], z[1], z[2]); but I'm sure there's a cleaner/more efficient way to do it? I've tried DT.ParseExact, but can't find a suitable format string to use.

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  • Fastest method in merging of the two: dicts vs lists

    - by tipu
    I'm doing some indexing and memory is sufficient but CPU isn't. So I have one huge dictionary and then a smaller dictionary I'm merging into the bigger one: big_dict = {"the" : {"1" : 1, "2" : 1, "3" : 1, "4" : 1, "5" : 1}} smaller_dict = {"the" : {"6" : 1, "7" : 1}} #after merging resulting_dict = {"the" : {"1" : 1, "2" : 1, "3" : 1, "4" : 1, "5" : 1, "6" : 1, "7" : 1}} My question is for the values in both dicts, should I use a dict (as displayed above) or list (as displayed below) when my priority is to use as much memory as possible to gain the most out of my CPU? For clarification, using a list would look like: big_dict = {"the" : [1, 2, 3, 4, 5]} smaller_dict = {"the" : [6,7]} #after merging resulting_dict = {"the" : [1, 2, 3, 4, 5, 6, 7]} Side note: The reason I'm using a dict nested into a dict rather than a set nested in a dict is because JSON won't let me do json.dumps because a set isn't key/value pairs, it's (as far as the JSON library is concerned) {"a", "series", "of", "keys"} Also, after choosing between using dict to a list, how would I go about implementing the most efficient, in terms of CPU, method of merging them? I appreciate the help.

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  • Should I use multiple threads in this situation? [Ruby]

    - by mr popo
    I'm opening multiple files and processing them, one line at a time. The files contain tokens separating the data, such that sometimes the processing of one file may have to wait for others to catch up to that same token. I was doing this initially with only one thread and an array indicating with true/false if the file should be read in the current iteration or if it should wait for some of the others to catch up. Would using threads make this simpler? More efficient? Does Ruby have a mechanism for this?

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  • Building a custom iterator.

    - by Isai
    I am making this class which is a custom Map based off a hash map. I have an add method where if you add an object the object will be the key, and its value will be 1 if the object is not currently in the list. However if you add object that is currently in the list its value will be bumped up by 1. So if I added 10 strings which were all the same, the key would be that string and the value will be 10. I understand in practice when I iterate through the map, there is actually only one object to iterate, however, I am trying to create a inner class that will define an iterator that will iterate the same object however many times its value is. I can do this by simply using for loops to construct an appropriate ArrayList and just create an iterator for that, but that is too inefficient. Is there an easy or more efficient way of doing this?

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  • I want to crop an image, draw a smaller size image without caching the images.... What is the best w

    - by rkbang
    Hello all, I am storing the images in database. I get the NSData and create an image from it. Now I want to crop or draw a smaller image of the existing image in database which I am getting from the querry. I dont want to cache the images since I am using them in bulk and want to release them as soon as the view being displayed where the images are used is popped up. Is there any efficient solution to make sure that images dont consume memory at the background once their use is over... I will appreciate the lines of code for this. Tnx in advance.

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  • Low-overhead way to access the memory space of a traced process?

    - by vovick
    Hello all. I'm looking for an efficient way to access(for both read and write operations) the memory space of my ptraced child process. The size of blocks being accessed may vary from several bytes up to several megabytes in size, so using the ptrace call with PTRACE_PEEKDATA and PTRACE_POKEDATA which read only one word at a time and switch context every time they're called seems like a pointless waste of resources. The only one alternative solution I could find, though, was the /proc/<pid>/mem file, but it has long since been made read only. Is there any other (relatively simple) way to do that job? The ideal solution would be to somehow share the address space of my child process with its parent and then use the simple memcpy call to copy data I need in both directions, but I have no clues how to do it and where to begin. Any ideas?

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  • Is it possible to scroll in isearch mode?

    - by Leo Alekseyev
    Is there a way to scroll through a document without exiting isearch mode? I have isearch-allow-scroll set to t, but that limits my scroll range to make sure the current isearch match is visible in the buffer. Ideally, I would like to be able to scroll with the mousewheel, having all the isearch matches highlighted as I scroll. I am aware of M-x occur, but a lot of the time simply being able to scroll in isearch mode would be more efficient (in addition, M-x occur does not play well with folding mode).

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  • What are the disadvantages of using a StringBuilder?

    - by stickman
    I know that StringBuilder is more efficient than a normal string when processing code which modifies the string value a lot because although strings act like value types, they are actually reference, which makes them immutable so every time we change it, we need to create a new reference in memory. My question is that, why doesn't .NET just use stringBuilder by default? There must be some disadvantages of it over just using String. Can anyone tell me what they are? The only thing I can think of is perhaps it is a heavier object and it takes more time to instantiate so if you aren't changing the string too much, this would override the benefits of StringBuilder

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  • HTML5 - Creating a canvas on top of an SVG(or other image)

    - by cawd
    The reason for asking this question is because I want to be able to draw an arrow between two svg images. I want to use canvas to create the arrows, so firstly I generate the svgs then place a canvas on top of them to be able to draw the arrows. I've tried using style=... but haven't had any luck as everytime I add the canvas element it just pushes my svg images to another pl If there's no easy way to do this I'll just create arrows using SVG, I figured it would be more efficient to use canvas if I had to do lots of arrows in a short amount of time.

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  • extracting string occurrence in c

    - by David78
    I have a string from a text file that look something like this: long_str = "returns between paragraphs 20102/34.23" - 9203 1232 "test" "basic HTML" Note: Quotes are part of the string. int match(char *long_str){ char * str; if ((str = strchr(long_str, '"')) != NULL) str++; // last " ? else return 1; return 0; } Using strstr I'm trying to get the whole substring between the last two quotes: "basic HTML". I'm just not quite sure what would be a good and efficient way of getting that match. I'm open to any other ideas on how to approach this. Thanks

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  • Actionscript 3.0 Get all instances of a class?

    - by Windbrand
    I got a ton of movieclips in a class. Is there a more efficient way to apply a function to every instance in the class other than this? var textArray:Array = [ interludes.interludeIntro.interludeBegin1, interludes.interludeIntro.interludeBegin2, interludes.interludeIntro.interludeBegin3, interludes.interludeIntro.interludeBegin4, interludes.interludeIntro.interludeBegin5, interludes.interludeIntro.interludeBegin6, interludes.interludeIntro.interludeBegin7, //... ... ... interludes.interludeIntro.interludeBegin15 ]; for each (var interludeText:MovieClip in interludeBeginText) { interludeText.alpha = 0 //clear all text first } Also for some reason this doesn't work: interludes.interludeIntro.alpha = 0; It permanently turns that class invisible, even if I try to make specific instances visible later with: interludes.interludeIntro.interludeBegin1.alpha = 1; I have NO idea why the above doesn't work. I want to turn every single instance in the class interludeIntro invisible, but I want to turn specific instances visible later. (btw I have no idea how to insert code on this website, pressing "code" doesn't do anything, so pardon the bad formatting)

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