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  • Is it good practice to name variables differently when defining more than one function?

    - by John
    For example, in this simple function where fun1 takes as input two numbers, adds them together and passes them to function 2 for printing the output. var1_in is local to each function, so is it OK to use the name var1_in in both functions, or is it better practice to call them different things? fun1 <- function (var1_in, var2_in) { var3 = var1_in + var2_in fun2(var3) } fun2 <- function (var1_in) { var4 = var1_in print(var4) }

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  • Is there a term for this concept, and does it exist in a static-typed language?

    - by Strilanc
    Recently I started noticing a repetition in some of my code. Of course, once you notice a repetition, it becomes grating. Which is why I'm asking this question. The idea is this: sometimes you write different versions of the same class: a raw version, a locked version, a read-only facade version, etc. These are common things to do to a class, but the translations are highly mechanical. Surround all the methods with lock acquires/releases, etc. In a dynamic language, you could write a function which did this to an instance of a class (eg. iterate over all the functions, replacing them with a version which acquires/releases a lock.). I think a good term for what I mean is 'reflected class'. You create a transformation which takes a class, and returns a modified-in-a-desired-way class. Synchronization is the easiest case, but there are others: make a class immutable [wrap methods so they clone, mutate the clone, and include it in the result], make a class readonly [assuming you can identify mutating methods], make a class appear to work with type A instead of type B, etc. The important part is that, in theory, these transformations make sense at compile-time. Even though an ActorModel<T> has methods which change depending on T, they depend on T in a specific way knowable at compile-time (ActorModel<T> methods would return a future of the original result type). I'm just wondering if this has been implemented in a language, and what it's called.

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  • How can I avoid mutable variables in Scala when using ZipInputStreams and ZipOutpuStreams?

    - by pr1001
    I'm trying to read a zip file, check that it has some required files, and then write all valid files out to another zip file. The basic introduction to java.util.zip has a lot of Java-isms and I'd love to make my code more Scala-native. Specifically, I'd like to avoid the use of vars. Here's what I have: val fos = new FileOutputStream("new.zip"); val zipOut = new ZipOutputStream(new BufferedOutputStream(fos)); while (zipIn.available == 1) { val entry = zipIn.getNextEntry if (entryIsValid(entry)) { val fos = new FileOutputStream("subdir/" + entry.getName()); val dest = new BufferedOutputStream(fos); // read data into the data Array var data: Array[Byte] = null var count = zip.read(data) while (count != -1) { dest.write(data, 0, count) count = zip.read(data) } dest.flush dest.close } }

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  • Is it possible to have a Shared/Static Dependency Property?

    - by Matt H.
    [using VB.NET, but I can easily read C# code in responses] I have a class called QuestionClipboard with ALL shared methods/properties. I previously had a QuesitonClipboard.doesClipboardHaveContent function that returned true/false if there was a Object on my 'clipboard'. I'd prefer to implement a Dependency Property so I can allow this true/false value to participate in data binding. The "GetValue(dp as DependencyProperty)" method requires an object instance, which would mean that my Property CAN'T be shared! Here is what the code would look like in my perfect world... Of course, the word "Shared" before the property declaration renders this code useless. Private Shared clipboardHasContentPropertyKey As DependencyPropertyKey = DependencyProperty.RegisterReadOnly("clipboardHasContent", GetType(Boolean), GetType(QuestionClipboard), _ New PropertyMetadata(False, Nothing, New CoerceValueCallback(AddressOf coerceClipboardHasContent))) Private Shared clipboardHasContentProperty As DependencyProperty = clipboardHasContentPropertyKey.DependencyProperty Public SHARED Property clipboardHasContent As Boolean Get Return GetValue(clipboardHasContentProperty) End Get Set(ByVal value As Boolean) SetValue(value) End Set End Property

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  • In what circumstances are instance variables declared as '_var' in 'use fields' private?

    - by Pedro Silva
    I'm trying to understand the behavior of the fields pragma, which I find poorly documented, regarding fields prefixed with underscores. This is what the documentation has to say about it: Field names that start with an underscore character are made private to the class and are not visible to subclasses. Inherited fields can be overridden but will generate a warning if used together with the -w switch. This is not consistent with its actual behavior, according to my test, below. Not only are _-prefixed fields visible within a subclass, they are visible within foreign classes as well (unless I don't get what 'visible' means). Also, directly accessing the restricted hash works fine. Where can I find more about the behavior of the fields pragma, short of going at the source code? { package Foo; use strict; use warnings; use fields qw/a _b __c/; sub new { my ( $class ) = @_; my Foo $self = fields::new($class); $self->a = 1; $self->b = 2; $self->c = 3; return $self; } sub a : lvalue { shift->{a} } sub b : lvalue { shift->{_b} } sub c : lvalue { shift->{__c} } } { package Bar; use base 'Foo'; use strict; use warnings; use Data::Dumper; my $o = Bar->new; print Dumper $o; ##$VAR1 = bless({'_b' => 2, '__c' => 3, 'a' => 1}, 'Foo'); $o->a = 4; $o->b = 5; $o->c = 6; print Dumper $o; ##$VAR1 = bless({'_b' => 5, '__c' => 6, 'a' => 4}, 'Foo'); $o->{a} = 7; $o->{_b} = 8; $o->{__c} = 9; print Dumper $o; ##$VAR1 = bless({'_b' => 8, '__c' => 9, 'a' => 7}, 'Foo'); }

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  • In what circumstances are instance variables declared as '_var' in 'use fields' readonly?

    - by Pedro Silva
    I'm trying to understand the behavior of the fields pragma, which I find poorly documented, regarding fields prefixed with underscores. This is what the documentation has to say about it: Field names that start with an underscore character are made private to the class and are not visible to subclasses. Inherited fields can be overridden but will generate a warning if used together with the -w switch. This is not consistent with its actual behavior, according to my test, below. Not only are _-prefixed fields visible within a subclass, they are visible within foreign classes as well (unless I don't get what 'visible' means). Also, directly accessing the restricted hash works fine. Where can I find more about the behavior of the fields pragma, short of going at the source code? { package Foo; use strict; use warnings; use fields qw/a _b __c/; sub new { my ( $class ) = @_; my Foo $self = fields::new($class); $self->a = 1; $self->b = 2; $self->c = 3; return $self; } sub a : lvalue { shift->{a} } sub b : lvalue { shift->{_b} } sub c : lvalue { shift->{__c} } } { package Bar; use base 'Foo'; use strict; use warnings; use Data::Dumper; my $o = Bar->new; print Dumper $o; ##$VAR1 = bless({'_b' => 2, '__c' => 3, 'a' => 1}, 'Foo'); $o->a = 4; $o->b = 5; $o->c = 6; print Dumper $o; ##$VAR1 = bless({'_b' => 5, '__c' => 6, 'a' => 4}, 'Foo'); $o->{a} = 7; $o->{_b} = 8; $o->{__c} = 9; print Dumper $o; ##$VAR1 = bless({'_b' => 8, '__c' => 9, 'a' => 7}, 'Foo'); }

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  • slowAES encryption and java descryption

    - by amnon
    Hi , I've tried to implement the same steps as discussed in AES .NET but with no success , i can't seem to get java and slowAes to play toghter ... attached is my code i'm sorry i can't add more this is my first time trying to deal with encryption would appreciate any help private static final String ALGORITHM = "AES"; private static final byte[] keyValue = getKeyBytes("12345678901234567890123456789012"); private static final byte[] INIT_VECTOR = new byte[16]; private static IvParameterSpec ivSpec = new IvParameterSpec(INIT_VECTOR); public static void main(String[] args) throws Exception { String encoded = encrypt("watson?"); System.out.println(encoded); } private static Key generateKey() throws Exception { Key key = new SecretKeySpec(keyValue, ALGORITHM); // SecretKeyFactory keyFactory = SecretKeyFactory.getInstance(ALGORITHM); // key = keyFactory.generateSecret(new DESKeySpec(keyValue)); return key; } private static byte[] getKeyBytes(String key) { byte[] hash = DigestUtils.sha(key); byte[] saltedHash = new byte[16]; System.arraycopy(hash, 0, saltedHash, 0, 16); return saltedHash; } public static String encrypt(String valueToEnc) throws Exception { Key key = generateKey(); Cipher c = Cipher.getInstance("AES/CBC/PKCS5Padding"); c.init(Cipher.ENCRYPT_MODE, key,ivSpec); byte[] encValue = c.doFinal(valueToEnc.getBytes()); String encryptedValue = new BASE64Encoder().encode(encValue); return encryptedValue; } public static String decrypt(String encryptedValue) throws Exception { Key key = generateKey(); Cipher c = Cipher.getInstance(ALGORITHM); c.init(Cipher.DECRYPT_MODE, key); byte[] decordedValue = new BASE64Decoder().decodeBuffer(encryptedValue); byte[] decValue = c.doFinal(decordedValue); String decryptedValue = new String(decValue); return decryptedValue; } the bytes returned are different thanks in advance .

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  • Is there a way to prevent an ASP.Net webapp from clearing out page variables on VB side?

    - by Chapso
    I have a webapp in ASP.Net with a VB codebehind. I need a List variable I have declared to persist as long as the person is on the page, but currently any time a control posts back to the code, everything is cleared out. I am completely new to ASP.net, so I have no idea if this is even possible. Can it be done with a Session variable? Those seem to me to be limited to base types, but I could be wrong.

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  • How do I split up a long value (32 bits) into four char variables (8bits) using C?

    - by Jordan S
    I have a 32 bit long variable, CurrentPosition, that I want to split up into 4, 8bit characters. How would I do that most efficiently in C? I am working with an 8bit MCU, 8051 architectecture. unsigned long CurrentPosition = 7654321; unsigned char CP1 = 0; unsigned char CP2 = 0; unsigned char CP3 = 0; unsigned char CP4 = 0; // What do I do next? Should I just reference the starting address of CurrentPosition with a pointer and then add 8 two that address four times? It is little Endian. ALSO I want CurrentPosition to remain unchanged.

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  • Should I cast variables that use a typdef'd type?

    - by mesorismo
    If I have something like: typedef int MyType; is it good practice to cast the operands of an operation if I do something like this: int x = 5; int y = 6; MyType a = (MyType)(x + y); I know that I don't need to do that but wondering if it's better for intent/documentation/readability concerns.

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  • How to get session variables from php server with Ajax function? (PHP HTML JS Ajax)

    - by Ole Jak
    so in my php I have something like this $_SESSION['opened'] = true; But It will not be set to true until user will perform some actions with some other html\php pages So I need on some Ajax function to be able get this session variable. And some PHP sample of function to get variable in form ready for Ajax to get it. so I need something to AJAX requesting to an action (to some simple php code) which will return a value from $_SESSION. How to do such thing?

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  • Why doesn't Rails' "errors.full_messages" replace attribute and message variables?

    - by tybro0103
    Having a strange problem with a rails model I just created. Here are my validations: validates_presence_of :from_name, :message => 'Please provide a from name.' validates_presence_of :from_email validates_presence_of :giftition_plan_id I'm having issues using errors.full_messages as well as f.error_messages in my form: g = Giftition.create g.errors.first => ["from_name", "Please provide a from name."] >> g.errors.full_messages => ["{{attribute}} {{message}}", "{{attribute}} {{message}}", "{{attribute}} {{message}}"] I'm just getting "{{attribute}} {{message}}". Any ideas? UPDATE: I've uninstalled rails 3 and all the gems that were installed with it and that made the problem go away. It's not a fix though... I would still like to have rails 3 installed.

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  • Can you pass _POST variables from 1 server to another?

    - by Dr. DOT
    I have a web form on an IIS server (has no PHP). I have a PHP script on a LAMP server. My _POST var array is coming up empty on the LAMP server. My suspicion is I cannot pass POST vars from 1 server to another but I would like to have that confirmed. Does anyone know the answer to this? If that's the case then I know I need to with use _GET vars in the URL's Query String or set a cookie (which I can do because both servers are config'd with the domain name). Thanks for your help.

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  • Is there a way to access Joomla 1.5 user variables (like user id) from a Flex 4 application using a PHP Data Service?

    - by Zachary G. Schroeder
    I have written a script (in two files) that correctly displays a Joomla user id, like this: //this is testy.php define( '_JEXEC', 1 ); define('JPATH_BASE', dirname(FILE)); define( 'DS', DIRECTORY_SEPARATOR ); require_once ( JPATH_BASE .DS.'includes'.DS.'defines.php' ); require_once ( JPATH_BASE .DS.'includes'.DS.'framework.php' ); $mainframe =& JFactory::getApplication('site'); $id = JFactory::getUser()-id; The above file is located in the Joomla root folder. The other file is in a different directory and is as follows: //this is testid.php include '../../joomla/testy.php'; echo $id; However, and here is the rub, when I change the "echo" to a "return" and put the second code snippet inside my Flex 4 Data Service script file, like this... function getUserId() { include '../../joomla/testy.php'; return $id; } ...I get a Flex error that says this: Fatal error: Class 'JRequest' not found in /var/www/html/joomla/libraries/joomla/import.php on line 33 I am extremely confused by this error and would appreciate any suggestions that the stackoverflow community may have. Thanks so much! Zach

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  • Cache an FTP connection via session variables for use via AJAX?

    - by Chad Johnson
    I'm working on a Ruby web Application that uses the Net::FTP library. One part of it allows users to interact with an FTP site via AJAX. When the user does something, and AJAX call is made, and then Ruby reconnects to the FTP server, performs an action, and outputs information. Every time the AJAX call is made, Ruby has to reconnect to the FTP server, and that's slow. Is there a way I could cache this FTP connection? I've tried caching in the session hash, but "We're sorry, but something went wrong" is displayed, and a TCP dump is outputted in my logs whenever I attempt to store it in the session hash. I haven't tried memcache yet. Any suggestions?

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