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  • problem adding object to hashtable

    - by daemonkid
    I am trying to call a class method dynamically depending on a condition. This is how I am doing it I have three classes implement a single interface interface IReadFile { string DoStuff(); } The three classes A,B,C implement the interface above. I am trying to add them to a hashtable with the code below _HashT.Add("a", new classA()); _HashT.Add("b", new classB()); _HashT.Add("c", new classC()); This compiles fine, but gives a runtime error.{Object reference not set to an instance of an object.} I was planning to return the correct class to the interface type depending on a parameter that matches the key value. say if I send in a. ClassA is returned to the interface type and the method is called. IReadFile Obj = (IReadFile )_HashT["a"].GetType(); obj.DoStuff(); How do I correct the part above where the objects need to be added to the hashtable? Or do I need to use a different approach? All the classes are in the same assembly and namespace. Thanks for your time.

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  • MySQL query does not return any data

    - by Alex L
    Hi, I need to retrieve data from a specific time period. The query works fine until I specify the time period. Is there something wrong with the way I specify time period? I know there are many entries within that time-frame. This query returns empty: SELECT stop_times.stop_id, STR_TO_DATE(stop_times.arrival_time, '%H:%i:%s') as stopTime, routes.route_short_name, routes.route_long_name, trips.trip_headsign FROM trips JOIN stop_times ON trips.trip_id = stop_times.trip_id JOIN routes ON routes.route_id = trips.route_id WHERE stop_times.stop_id = 5508 HAVING stopTime BETWEEN DATE_SUB(stopTime,INTERVAL 1 MINUTE) AND DATE_ADD(stopTime,INTERVAL 20 MINUTE); Here is it's EXPLAIN: +----+-------------+------------+--------+------------------+---------+---------+-------------------------------+------+-------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+------------+--------+------------------+---------+---------+-------------------------------+------+-------------+ | 1 | SIMPLE | stop_times | ref | trip_id,stop_id | stop_id | 5 | const | 605 | Using where | | 1 | SIMPLE | trips | eq_ref | PRIMARY,route_id | PRIMARY | 4 | wmata_gtfs.stop_times.trip_id | 1 | | | 1 | SIMPLE | routes | eq_ref | PRIMARY | PRIMARY | 4 | wmata_gtfs.trips.route_id | 1 | | +----+-------------+------------+--------+------------------+---------+---------+-------------------------------+------+-------------+ 3 rows in set (0.00 sec) The query works if I remove the HAVING clause (don't specify time range). Returns: +---------+----------+------------------+-----------------+---------------+ | stop_id | stopTime | route_short_name | route_long_name | trip_headsign | +---------+----------+------------------+-----------------+---------------+ | 5508 | 06:31:00 | "80" | "" | "FORT TOTTEN" | | 5508 | 06:57:00 | "80" | "" | "FORT TOTTEN" | | 5508 | 07:23:00 | "80" | "" | "FORT TOTTEN" | | 5508 | 07:49:00 | "80" | "" | "FORT TOTTEN" | | 5508 | 08:15:00 | "80" | "" | "FORT TOTTEN" | | 5508 | 08:41:00 | "80" | "" | "FORT TOTTEN" | | 5508 | 09:08:00 | "80" | "" | "FORT TOTTEN" | I am using Google Transit format Data loaded into MySQL. The query is supposed to provide stop times and bus routes for a given bus stop. For a bus stop, I am trying to get: Route Name Bus Name Bus Direction (headsign) Stop time The results should be limited only to buses times from 1 min ago to 20 min from now. Please let me know if you could help.

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  • Decrypting a string in C# 3.5 which was encrypted with openssl in php 5.3.2

    - by panny
    Hi everyone, maybe someone can clear me up. I have been surfing on this a while now. I used openssl from console to create a root certificate for me (privatekey.pem, publickey.pem, mycert.pem, mycertprivatekey.pfx). See the end of this text on how. The problem is still to get a string encrypted on the PHP side to be decrypted on the C# side with RSACryptoServiceProvider. Any ideas? PHP side I used the publickey.pem to read it into php: $server_public_key = openssl_pkey_get_public(file_get_contents("C:\publickey.pem")); // rsa encrypt openssl_public_encrypt("123", $encrypted, $server_public_key); and the privatekey.pem to check if it works: openssl_private_decrypt($encrypted, $decrypted, openssl_get_privatekey(file_get_contents("C:\privatekey.pem"))); Coming to the conclusion, that encryption/decryption works fine on the php side with these openssl root certificate files. C# side In same manner I read the keys into a .net C# console program: X509Certificate2 myCert2 = new X509Certificate2(); RSACryptoServiceProvider rsa = new RSACryptoServiceProvider(); try { myCert2 = new X509Certificate2(@"C:\mycertprivatekey.pfx"); rsa = (RSACryptoServiceProvider)myCert2.PrivateKey; } catch (Exception e) { } string t = Convert.ToString(rsa.Decrypt(rsa.Encrypt(test, false), false)); coming to the point, that encryption/decryption works fine on the c# side with these openssl root certificate files. key generation on unix 1) openssl req -x509 -nodes -days 3650 -newkey rsa:1024 -keyout privatekey.pem -out mycert.pem 2) openssl rsa -in privatekey.pem -pubout -out publickey.pem 3) openssl pkcs12 -export -out mycertprivatekey.pfx -in mycert.pem -inkey privatekey.pem -name "my certificate"

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  • What is wrong with accessing DBI directly?

    - by canavanin
    Hi everyone! I'm currently reading Effective Perl Programming (2nd edition). I have come across a piece of code which was described as being poorly written, but I don't yet understand what's so bad about it, or how it should be improved. It would be great if someone could explain the matter to me. Here's the code in question: sub sum_values_per_key { my ( $class, $dsn, $user, $password, $parameters ) = @_; my %results; my $dbh = DBI->connect( $dsn, $user, $password, $parameters ); my $sth = $dbh->prepare( 'select key, calculate(value) from my_table'); $sth->execute(); # ... fill %results ... $sth->finish(); $dbh->disconnect(); return \%results; } The example comes from the chapter on testing your code (p. 324/325). The sentence that has left me wondering about how to improve the code is the following: Since the code was poorly written and accesses DBI directly, you'll have to create a fake DBI object to stand in for the real thing. I have probably not understood a lot of what the book has so far been trying to teach me, or I have skipped the section relevant for understanding what's bad practice about the above code... Well, thanks in advance for your help!

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  • need to display info for user within active-directory

    - by Brad
    The following code will search for the user within the domain controller, but I want to display the info of each thing noted within the justthese variable: "displayname","mail","samaccountname","sn","givenname","department","telephonenumber" $dn = "dc=xxx,dc=xxx"; $justthese = array("displayname","mail","samaccountname","sn","givenname","department","telephonenumber"); $sr=ldap_search($ldapconn, $dn,'SAMAccountName=username', $justthese); $info = ldap_get_entries($ldapconn, $sr); echo "<h3>".$info["count"]." entries returned</h3>"; foreach($justthese as $key=>$value){ print '<p><strong>'.$value.'</strong></p>'; } It displays each item within the $justthese array, I want to display the info for that user for each thing noted in $justthese array. Right now it outputs it like this: displayname mail samaccountname sn givenname department telephonenumber I want it to have the actual data to the right of it, which I know I am doing something wrong with the foreach loop, any help is appreciated. So it'd look like this displayname Chuck mail [email protected] samaccountname chucknorris sn chuckisthebest givenname Chuck Norris department Security telephonenumber 555-555-5555

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  • Checking if any of a list of values falls within a table of ranges

    - by Conspicuous Compiler
    I'm looking to check whether any of a list of integers fall in a list of ranges. The ranges are defined in a table defined something like: # Extra Type Field Default Null Key 0 int(11) rangeid 0 NO PRI 1 int(11) max 0 NO MUL 2 int(11) min 0 NO MUL Using MySQL 5.1 and Perl 5.10. I can check whether a single value, say 7, is in any of the ranges with a statement like SELECT 1 FROM range WHERE 7 BETWEEN min AND max If 7 is in any of those ranges, I get a single row back. If it isn't, no rows are returned. Now I have a list of, say, 50 of these values, not stored in a table at present. I assemble them using map: my $value_list = '(' . ( join ', ', map { int $_ } @values ) . ')' ; I want to see if any of the items in the list fall inside of any of the ranges, but am not particularly concerned with which number nor which range. I'd like to use a syntax such as: SELECT 1 FROM range WHERE (1, 2, 3, 4, 5, 6, 7, 42, 309, 10000) BETWEEN min AND max MySQL kindly chastises me for such syntax: Operand should contain 1 column(s) I pinged #mysql who were quite helpful. However, having already written this up by the time they responded and thinking it'd be helpful to fix the answer in a more permanent medium, I figured I'd post the question anyhow. Maybe SO will provide a different solution?

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  • Can't seem to sign AWS Cloud Front URL properly

    - by Joe Corkery
    Hi everybody, I found a lot of detailed examples online on how to sign an Amazon CloudFront URL for private content. Unfortunately, whenever I implement these examples my URL doesn't seem to work. The resource path is correct because I can download the file when it is set for world read, but the URL doesn't work when set just for authorized users. The PHP code I am using is below. If anybody has any insights as to what I might be doing wrong (I'm guessing it is something obvious that I am just not seeing right now), it would be greatly appreciated. function urlCloudFront($resource) { $AWS_CF_KEY = 'APKA...'; $priv_key = file_get_contents(path_to_pem_file); $pkeyid = openssl_get_privatekey($priv_key); $expires = strtotime("+ 3 hours"); $policy_str = '{"Statement":[{"Resource":"'.$resource.'","Condition":{"DateLessThan":{"AWS:EpochTime":'.$expires.'}}}]}'; $policy_str = trim( preg_replace( '/\s+/', '', $policy_str ) ); $res = openssl_sign($policy_str, $signature, $pkeyid, OPENSSL_ALGO_SHA1); $signature_base64 = (base64_encode($signature)); $repl = array('+' => '-','=' => '_','/' => '~'); $signature_base64 = strtr($signature_base64,$repl); $url = $resource . '?Expires=' .$expires. '&Signature=' . $signature_base64 . '&Key-Pair-Id='. $AWS_CF_KEY; print '<p><A href="' .$url. '">Download VIDA (CloudFrount)</A>'; } urlCloudFront("http://mydistcloud.cloudfront.net/mydir/myfile.tar.gz"); Thanks.

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  • Simple encryption - Sum of Hashes in C

    - by Dogbert
    I am attempting to demonstrate a simple proof of concept with respect to a vulnerability in a piece of code in a game written in C. Let's say that we want to validate a character login. The login is handled by the user choosing n items, (let's just assume n=5 for now) from a graphical menu. The items are all medieval themed: eg: _______________________________ | | | | | Bow | Sword | Staff | |-----------|-----------|-------| | Shield | Potion | Gold | |___________|___________|_______| The user must click on each item, then choose a number for each item. The validation algorithm then does the following: Determines which items were selected Drops each string to lowercase (ie: Bow becomes bow, etc) Calculates a simple string hash for each string (ie: `bow = b=2, o=15, w=23, sum = (2+15+23=40) Multiplies the hash by the value the user selected for the corresponding item; This new value is called the key Sums together the keys for each of the selected items; this is the final validation hash IMPORTANT: The validator will accept this hash, along with non-zero multiples of it (ie: if the final hash equals 1111, then 2222, 3333, 8888, etc are also valid). So, for example, let's say I select: Bow (1) Sword (2) Staff (10) Shield (1) Potion (6) The algorithm drops each of these strings to lowercase, calculates their string hashes, multiplies that hash by the number selected for each string, then sums these keys together. eg: Final_Validation_Hash = 1*HASH(Bow) + 2*HASH(Sword) + 10*HASH(Staff) + 1*HASH(Shield) + 6*HASH(Potion) By application of Euler's Method, I plan to demonstrate that these hashes are not unique, and want to devise a simple application to prove it. in my case, for 5 items, I would essentially be trying to calculate: (B)(y) = (A_1)(x_1) + (A_2)(x_2) + (A_3)(x_3) + (A_4)(x_4) + (A_5)(x_5) Where: B is arbitrary A_j are the selected coefficients/values for each string/category x_j are the hash values for each string/category y is the final validation hash (eg: 1111 above) B,y,A_j,x_j are all discrete-valued, positive, and non-zero (ie: natural numbers) Can someone either assist me in solving this problem or point me to a similar example (ie: code, worked out equations, etc)? I just need to solve the final step (ie: (B)(Y) = ...). Thank you all in advance.

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  • Multiple inequality conditions (range queries) in NoSQL

    - by pableu
    Hi, I have an application where I'd like to use a NoSQL database, but I still want to do range queries over two different properties, for example select all entries between times T1 and T2 where the noiselevel is smaller than X. On the other hand, I would like to use a NoSQL/Key-Value store because my data is very sparse and diverse, and I do not want to create new tables for every new datatype that I might come across. I know that you cannot use multiple inequality filters for the Google Datastore (source). I also know that this feature is coming (according to this). I know that this is also not possible in CouchDB (source). I think I also more or less understand why this is the case. Now, this makes me wonder.. Is that the case with all NoSQL databases? Can other NoSQL systems make range queries over two different properties? How about, for example, Mongo DB? I've looked in the Documentation, but the only thing I've found was the following snippet in their docu: Note that any of the operators on this page can be combined in the same query document. For example, to find all document where j is not equal to 3 and k is greater than 10, you'd query like so: db.things.find({j: {$ne: 3}, k: {$gt: 10} }); So they use greater-than and not-equal on two different properties. They don't say anything about two inequalities ;-) Any input and enlightenment is welcome :-)

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  • python gui events out of order

    - by dave
    from Tkinter import * from tkMessageBox import * class Gui: def __init__(self, root): self.container = Frame(root) self.container.grid() self.inputText = Text(self.container, width=50, height=8) self.outputText = Text(self.container, width=50, height=8, bg='#E0E0E0', state=DISABLED) self.inputText.grid(row=0, column=0) self.outputText.grid(row=0, column=1) self.inputText.bind("<Key>", self.translate) def translate(self, event): input = self.inputText.get(0.0, END) output = self.outputText.get(0.0, END) self.outputText.config(state=NORMAL) self.outputText.delete(0.0, END) self.outputText.insert(INSERT, input) self.outputText.config(state=DISABLED) showinfo(message="Input: %s characters\nOutput: %s characters" % (len(input), len(input))) root = Tk() #toplevel object app = Gui(root) #call to the class where gui is defined root.mainloop() #enter event loop Working on a gui in tkinter I'm a little confused as to the sequence the event handlers are run. If you run the above code you'll hopefully see... 1) Editing the text widget triggers the event handler but it seems to fire it off without registering the actual change, 2) Even when the text widget is cleared (ie, keep pressing BackSpace) it still seems to have a one character length string, 3) The output widget only receives its update when the NEXT event trigger is fired despite the fact the data came on the previous event. Is this just how bindings work in tkinter or am i missing something here? The behaviour i would like when updating the input widget is: 1) Show the change, 2) Enter event handler, 3) Update output widget, 4) Show message box.

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  • Wnat is the preferred method of building extremely lightweight business object / DAL now that I have

    - by Seth Spearman
    Hello, I have completed a simple database for a project. Only 6tables. Of the 6, one is a "lookup" table. There is one "master" table that is the driver for the system. It is referenced as a foreign key by the other four tables. Give that this step is completed. What is the FASTEST, EASIEST way to create POCOs/BizObjects that can load load the data and the child data. Here are my CAVEATS. *I don't want to spend more than 30-60 minutes learning how? *There is very little biz logic needed in the POCOs. They will pretty much load data. Don't even really need to write back data. *I already know CSLA (up to version 3) but I feel that is overkill for this little project. *Nevertheless, I would love it if it ROOT objects could have collection classes that contain the CHILD objects as in CSLA...but again, without using CSLA. *Please give the answer for .NET 35 but also if I was restricted to only use .NET 20. *Ideally I could just point a tool at the database and the POCOs would be genn'ed. *FREE Just curious what you guys use for this kind of scenario. I understand that this question is subjective but I want to hear a variety of answers. Seth

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  • No Hibernate Exception on the same insert of data

    - by Mark Estrada
    Hi All, Hibernate Newbie here. I am quite unsure why I am not getting any exception when I am executing below code. On first attempt, this code creates the Book Entry on my Book Table. But my concern is that when I execute below code again, no error was pop out by Hibernate. I was in fact expecting some sort of Violation of Primary Key Constraints as what I have bee doing in JDBC code. public class BookDao { public void createBook(Book bookObj) { Session session = HibernateUtil.getSessionFactory() .getCurrentSession(); session.beginTransaction(); session.saveOrUpdate(bookObj); session.getTransaction().commit(); } } public class HibernateUtil { private static final SessionFactory sessionFactory = buildSessionFactory(); private static SessionFactory buildSessionFactory() { try { // Create the SessionFactory from hibernate.cfg.xml return new AnnotationConfiguration().configure() .buildSessionFactory(); } catch (Throwable ex) { // Make sure you log the exception, as it might be swallowed ex.printStackTrace(); throw new ExceptionInInitializerError(ex); } } public static SessionFactory getSessionFactory() { return sessionFactory; } } public class BookDBStarter { public static void main(String[] args) { Book bookHF = new Book(); bookHF.setIsbn("HF-12345"); bookHF.setName("Head First HTML"); bookHF.setPublishDate(new Date()); BookDao daoBook = new BookDao(); daoBook.createBook(bookHF); } } Is this normal hibernate way? And how will I know if my insert is successful? Any thoughts?

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  • How to: Simulating keystroke inputs in shell to an app running in an embedded target

    - by fzkl
    I am writing an automation script that runs on an embedded linux target. A part of the script involves running an app on the target and obtaining some data from the stdout. Stdout here is the ssh terminal connection I have to the target. However, this data is available on the stdout only if certain keys are pressed and the key press has to be done on the keyboard connected to the embedded target and not on the host system from which I have ssh'd into the target. Is there any way to simulate this? Edit: Elaborating on what I need - I have an OpenGL app that I run on the embedded linux (works like regular linux) target. This displays some graphics on the embedded system's display device. Pressing f on the keyboard connected to the target outputs the fps data onto the ssh terminal from which I control the target. Since I am automating the process of running this OpenGL app and obtaining the fps scores, I can't expect a keyboard to be connected to the target let alone expect a user to input a keystroke on the embedded target keyboard. How do I go about this? Thanks.

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  • Why are symbols not frozen strings?

    - by Alex Chaffee
    I understand the theoretical difference between Strings and Symbols. I understand that Symbols are meant to represent a concept or a name or an identifier or a label or a key, and Strings are a bag of characters. I understand that Strings are mutable and transient, where Symbols are immutable and permanent. I even like how Symbols look different from Strings in my text editor. What bothers me is that practically speaking, Symbols are so similar to Strings that the fact that they're not implemented as Strings causes a lot of headaches. They don't even support duck-typing or implicit coercion, unlike the other famous "the same but different" couple, Float and Fixnum. The mere existence of HashWithIndifferentAccess, and its rampant use in Rails and other frameworks, demonstrates that there's a problem here, an itch that needs to be scratched. Can anyone tell me a practical reason why Symbols should not be frozen Strings? Other than "because that's how it's always been done" (historical) or "because symbols are not strings" (begging the question). Consider the following astonishing behavior: :apple == "apple" #=> false, should be true :apple.hash == "apple".hash #=> false, should be true {apples: 10}["apples"] #=> nil, should be 10 {"apples" => 10}[:apples] #=> nil, should be 10 :apple.object_id == "apple".object_id #=> false, but that's actually fine All it would take to make the next generation of Rubyists less confused is this: class Symbol < String def initialize *args super self.freeze end (and a lot of other library-level hacking, but still, not too complicated) See also: http://onestepback.org/index.cgi/Tech/Ruby/SymbolsAreNotImmutableStrings.red http://www.randomhacks.net/articles/2007/01/20/13-ways-of-looking-at-a-ruby-symbol Why does my code break when using a hash symbol, instead of a hash string? Why use symbols as hash keys in Ruby? What are symbols and how do we use them? Ruby Symbols vs Strings in Hashes Can't get the hang of symbols in Ruby

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  • Does anyone know why my maps only show grid

    - by NickTFried
    I've doubled checked my API key is right and that is right I doubled checked that it was correct. Here is my source and XML could anyone check to see what is wrong. Also I make sure I have internet. <?xml version="1.0" encoding="utf-8"?> <uses-permission android:name="android.permissions.INTERNET"/> <uses-permission android:name="android.permissions.ACCESS_FINE_LOCATION"/> <application android:icon="@drawable/icon" android:label="@string/app_name"> <uses-library android:name="com.google.android.maps" /> <activity android:name=".CadetCommand" android:label="@string/app_name"> <intent-filter> <action android:name="android.intent.action.MAIN" /> <category android:name="android.intent.category.LAUNCHER" /> </intent-filter> </activity> <activity android:name="RedLight"></activity> <activity android:name="PTCalculator"></activity> <activity android:name="LandNav"></activity> </application> <uses-sdk android:minSdkVersion="4"/> package edu.elon.cs.mobile; import com.google.android.maps.MapActivity; import com.google.android.maps.MapView; import android.os.Bundle; public class LandNav extends MapActivity{ public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.landnav); } @Override protected boolean isRouteDisplayed() { return false; } }

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  • How can I emulate Vim's * search in GNU Emacs?

    - by rq
    In Vim the * key in normal mode searches for the word under the cursor. In GNU Emacs the closest native equivalent would be: C-s C-w But that isn't quite the same. It opens up the incremental search mini buffer and copies from the cursor in the current buffer to the end of the word. In Vim you'd search for the whole word, even if you are in the middle of the word when you press *. I've cooked up a bit of elisp to do something similar: (defun find-word-under-cursor (arg) (interactive "p") (if (looking-at "\\<") () (re-search-backward "\\<" (point-min))) (isearch-forward)) That trots backwards to the start of the word before firing up isearch. I've bound it to C-+, which is easy to type on my keyboard and similar to *, so when I type C-+ C-w it copies from the start of the word to the search mini-buffer. However, this still isn't perfect. Ideally it would regexp search for "\<" word "\>" to not show partial matches (searching for the word "bar" shouldn't match "foobar", just "bar" on its own). I tried using search-forward-regexp and concat'ing \ but this doesn't wrap in the file, doesn't highlight matches and is generally pretty lame. An isearch-* function seems the best bet, but these don't behave well when scripted. Any ideas? Can anyone offer any improvements to the bit of elisp? Or is there some other way that I've overlooked?

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  • copy rows before updating them to preserve archive in Postgres

    - by punkish
    I am experimenting with creating a table that keeps a version of every row. The idea is to be able to query for how the rows were at any point in time even if the query has JOINs. Consider a system where the primary resource is books, that is, books are queried for, and author info comes along for the ride CREATE TABLE authors ( author_id INTEGER NOT NULL, version INTEGER NOT NULL CHECK (version > 0), author_name TEXT, is_active BOOLEAN DEFAULT '1', modified_on TIMESTAMP DEFAULT CURRENT_TIMESTAMP, PRIMARY KEY (author_id, version) ) INSERT INTO authors (author_id, version, author_name) VALUES (1, 1, 'John'), (2, 1, 'Jack'), (3, 1, 'Ernest'); I would like to be able to update the above like so UPDATE authors SET author_name = 'Jack K' WHERE author_id = 1; and end up with 2, 1, Jack, t, 2012-03-29 21:35:00 2, 2, Jack K, t, 2012-03-29 21:37:40 which I can then query with SELECT author_name, modified_on FROM authors WHERE author_id = 2 AND modified_on < '2012-03-29 21:37:00' ORDER BY version DESC LIMIT 1; to get 2, 1, Jack, t, 2012-03-29 21:35:00 Something like the following doesn't really work CREATE OR REPLACE FUNCTION archive_authors() RETURNS TRIGGER AS $archive_author$ BEGIN IF (TG_OP = 'UPDATE') THEN -- The following fails because author_id,version PK already exists INSERT INTO authors (author_id, version, author_name) VALUES (OLD.author_id, OLD.version, OLD.author_name); UPDATE authors SET version = OLD.version + 1 WHERE author_id = OLD.author_id AND version = OLD.version; RETURN NEW; END IF; RETURN NULL; -- result is ignored since this is an AFTER trigger END; $archive_author$ LANGUAGE plpgsql; CREATE TRIGGER archive_author AFTER UPDATE OR DELETE ON authors FOR EACH ROW EXECUTE PROCEDURE archive_authors(); How can I achieve the above? Or, is there a better way to accomplish this? Ideally, I would prefer to not create a shadow table to store the archived rows.

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  • Time complexity to fill hash table (homework)?

    - by Heathcliff
    This is a homework question, but I think there's something missing from it. It asks: Provide a sequence of m keys to fill a hash table implemented with linear probing, such that the time to fill it is minimum. And then Provide another sequence of m keys, but such that the time fill it is maximum. Repeat these two questions if the hash table implements quadratic probing I can only assume that the hash table has size m, both because it's the only number given and because we have been using that letter to address a hash table size before when describing the load factor. But I can't think of any sequence to do the first without knowing the hash function that hashes the sequence into the table. If it is a bad hash function, such that, for instance, it hashes every entry to the same index, then both the minimum and maximum time to fill it will take O(n) time, regardless of what the sequence looks like. And in the average case, where I assume the hash function is OK, how am I suppossed to know how long it will take for that hash function to fill the table? Aren't these questions linked to the hash function stronger than they are to the sequence that is hashed? As for the second question, I can assume that, regardless of the hash function, a sequence of size m with the same key repeated m-times will provide the maximum time, because it will cause linear probing from the second entry on. I think that will take O(n) time. Is that correct? Thanks

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  • Node-webkit works on Mac, crashes and can't load module on Windows

    - by user756201
    I've created a full node-webkit app that works fine on the Mac OSX version of node-webkit. Everything works, it loads a key external nodeJS module (marked), and the world is good. However, when I try to run the app on the Windows version of Node-webkit as described in the Wiki, the app crashes immediately (in fact, it crashes immediately when I try all the options: dragging a folder onto nw.exe, dragging an app.nw compressed folder, and running both from the command line). The only thing that gets me closer is opening nw.exe and then pointing the node-webkit location bar to the index file. Then I get this error: Uncaught node.js Error Error: Cannot find module 'marked' I tried commenting out the code that requires marked: var marked = require('marked'); That returns the app to crashing immediately. I assumed it was because of context issues between node.js and the node-webkit browser, but those seem to not be at fault since I tried this suggestion to make sure it finds the correct file for the marked module...went right back to immediate crashing. I'm out of ideas because the crashes don't seem to leave me any way of knowing what the error was.

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  • What are the skills a Drupal Developer needs?

    - by hfidgen
    I'm trying to write out a list of key Drupal competencies, mainly so I can confirm what I know, don't know and don't know I don't know. (Thanks D. Rumsfeld for that quote!) I think some of these are really broad, for instance there's quite a difference between making a functional theme and creating a theme with good SEO, load times and so on, but I'm hoping you could assume that a half decent web developer would look after that anyway. Just interested to see what people here feel is also important. Able to install Drupal on a server (pretty obvious). Able to research and install modules to meet project requirements Able to configure all the basic modules and core settings to get a site running Able to create a custom Theme from scratch which validates with good HTML/CSS and also pays attention to usability and accessibility. (Whilst still looking kick-ass). Able to use Hooks in the theme template.php to alter forms, page layout and other core functionality Can make forms from scratch using the API - with validation and posting back to the DB/email Can use Views to create blocks or pages, use php snippets as arguments, etc. Can create custom modules from scratch utilising core hooks and other hooks.

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  • Should onSaveInstanceState save the "enabledness" of the views?

    - by neutrino
    Hi there, I have a preferences activity where I can change the language and the theme of my application. From there I return to the previous activity via the Back key, and I want to recreate the activity. I've managed to do that by reinitializing the layout in onResume and also calling onRestoreInstanceState from there. All the views are restored properly, with checkboxes checked if needed, edittexts filled with texts I left there previously. But I also have a button which is initially disabled, and becomes enabled only when a radiobutton is checked. The problem with it is the following: I check the radiobutton, the button becomes enabled. Then I go to settings, change the theme there, and return to the first activity. When I arrive there, the radiobutton is still checked, but the button is disabled. So it seems that the enabled/disabled state isn't being saved into the bundle, which seems counterintuitive. And I haven't found any code in the Android source that does this, too. Am I missing something, or do I have to write my own code for that?

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  • How do I relate two models/tables in Django based on non primary non unique keys?

    - by wizard
    I've got two tables that I need to relate on a single field po_num. The data is imported from another source so while I have a little bit of control over what the tables look like but I can't change them too much. What I want to do is relate these two models so I can look up one from the other based on the po_num fields. What I really need to do is join the two tables so I can do a where on a count of the related table. I would like to do filter for all Order objects that have 0 related EDI856 objects. I tried adding a foreign key to the Order model and specified the db_column and to_fields as po_num but django didn't like that the fact that Edi856.po_num wasn't unique. Here are the important fields of my current models that let me display but not filter for the data that I want. class Edi856(models.Model): po_num = models.CharField(max_length=90, db_index=True ) class Order(models.Model): po_num = models.CharField(max_length=90, db_index=True) def in_edi(self): '''Has the edi been processed?''' return Edi856.objects.filter(po_num = self.po_num).count() Thanks for taking the time to read about my problem. I'm not sure what to do from here.

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  • MySQL "OR MATCH" hangs (very slow) on multiple tables

    - by Kerry
    After learning how to do MySQL Full-Text search, the recommended solution for multiple tables was OR MATCH and then do the other database call. You can see that in my query below. When I do this, it just gets stuck in a "busy" state, and I can't access the MySQL database. SELECT a.`product_id`, a.`name`, a.`slug`, a.`description`, b.`list_price`, b.`price`, c.`image`, c.`swatch`, e.`name` AS industry, MATCH( a.`name`, a.`sku`, a.`description` ) AGAINST ( '%s' IN BOOLEAN MODE ) AS relevance FROM `products` AS a LEFT JOIN `website_products` AS b ON (a.`product_id` = b.`product_id`) LEFT JOIN ( SELECT `product_id`, `image`, `swatch` FROM `product_images` WHERE `sequence` = 0) AS c ON (a.`product_id` = c.`product_id`) LEFT JOIN `brands` AS d ON (a.`brand_id` = d.`brand_id`) INNER JOIN `industries` AS e ON (a.`industry_id` = e.`industry_id`) WHERE b.`website_id` = %d AND b.`status` = %d AND b.`active` = %d AND MATCH( a.`name`, a.`sku`, a.`description` ) AGAINST ( '%s' IN BOOLEAN MODE ) OR MATCH ( d.`name` ) AGAINST ( '%s' IN BOOLEAN MODE ) GROUP BY a.`product_id` ORDER BY relevance DESC LIMIT 0, 9 Any help would be greatly appreciated. EDIT All the tables involved are MyISAM, utf8_general_ci. Here's the EXPLAIN SELECT statement: id select_type table type possible_keys key key_len ref rows Extra 1 PRIMARY a ALL NULL NULL NULL NULL 16076 Using temporary; Using filesort 1 PRIMARY b ref product_id product_id 4 database.a.product_id 2 1 PRIMARY e eq_ref PRIMARY PRIMARY 4 database.a.industry_id 1 1 PRIMARY <derived2> ALL NULL NULL NULL NULL 23261 1 PRIMARY d eq_ref PRIMARY PRIMARY 4 database.a.brand_id 1 Using where 2 DERIVED product_images ALL NULL NULL NULL NULL 25933 Using where I don't know how to make that look neater -- sorry about that UPDATE it returns the query after 196 seconds (I think correctly). The query without multiple tables takes about .56 seconds (which I know is really slow, we plan on changing to solr or sphinx soon), but 196 seconds?? If we could add a number to the relevance if it was in the brand name ( d.name ), that would also work

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  • Help me write my LISP :) LISP environments, Ruby Hashes...

    - by MikeC8
    I'm implementing a rudimentary version of LISP in Ruby just in order to familiarize myself with some concepts. I'm basing my implementation off of Peter Norvig's Lispy (http://norvig.com/lispy.html). There's something I'm missing here though, and I'd appreciate some help... He subclasses Python's dict as follows: class Env(dict): "An environment: a dict of {'var':val} pairs, with an outer Env." def __init__(self, parms=(), args=(), outer=None): self.update(zip(parms,args)) self.outer = outer def find(self, var): "Find the innermost Env where var appears." return self if var in self else self.outer.find(var) He then goes on to explain why he does this rather than just using a dict. However, for some reason, his explanation keeps passing in through my eyes and out through the back of my head. Why not use a dict, and then inside the eval function, when a new "sub-environment" needs to be created, just take the existing dict and update the key/value pairs that need to be updated, and pass that new dict into the next eval? Won't the Python interpreter keep track of the previous "outer" envs? And won't the nature of the recursion ensure that the values are pulled out from "inner" to "outer"? I'm using Ruby, and I tried to implement things this way. Something's not working though, and it might be because of this, or perhaps not. Here's my eval function, env being a regular Hash: def eval(x, env = $global_env) ........ elsif x[0] == "lambda" then ->(*args) { eval(x[2], env.merge(Hash[*x[1].zip(args).flatten(1)])) } ........ end The line that matters of course is the "lambda" one. If there is a difference, what's importantly different between what I'm doing here and what Norvig did with his Env class? If there's no difference, then perhaps someone can enlighten me as to why Norvig uses the Env class. Thanks :)

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  • Which pdf elements could cause crashes?

    - by Felixyz
    This is a very general question but it's based on a specific problem. I've created a pdf reader app for the iPad and it works fine except for certain pdf pages which always crash the app. We now found out that the very same pages cause Safari to crash as well, so as I had started to suspect the problem is somewhere in Apple's pdf rendering code. From what I have been able to see, the crashing pages cause the rendering libraries to start allocating memory like mad until the app is killed. I have nothing else to help me pinpoint what triggers this process. It doesn't necessarily happen with the largest documents, or the ones with the most shapes. In fact, we haven't found any parameter that helps us predict which pages will crash and which not. Now we just discovered that running the pages through a consumer program that lets you merge docs gets rid of the problem, but I haven't been able to detect which attribute or element it is that is the key. Changing documents by hand is also not an option for us in the long run. We need to run an automated process on our server. I'm hoping someone with deeper knowledge about the pdf file format would be able to point me in a reasonable direction to look for document features that could cause this kind of behavior. All I've found so far is something about JBIG2 images, and I don't think we have any of those.

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