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  • How are variables bound to the body of a define_method?

    - by Chris
    While trying to brush up my Ruby skills I keep running across this case which I can't figure out an explanation for by just reading the API docs. An explanation would be greatly appreciated. Here's the example code: for name in [ :new, :create, :destroy ] define_method("test_#{name}") do puts name end end What I want/expect to happen is that the name variable will be bound to the block given to define_method and that when #test_new is called it will output "new". Instead each defined method outputs "destroy" -- the last value assigned to the name variable. What am I misunderstanding about define_method and its blocks? Thanks!

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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 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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  • Mutable global variables don't get hide in python functions, right?

    - by aXqd
    Please see the following code: def good(): foo[0] = 9 # why this foo isn't local variable who hides the global one def bad(): foo = [9, 2, 3] # foo is local, who hides the global one for func in [good, bad]: foo = [1,2,3] print('Before "{}": {}'.format(func.__name__, foo)) func() print('After "{}": {}'.format(func.__name__, foo)) The result is as below: # python3 foo.py Before "good": [1, 2, 3] After "good": [9, 2, 3] Before "bad" : [1, 2, 3] After "bad" : [1, 2, 3]

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  • Who use class variables in SOAP calls with Savon?

    - by Steffen Roller
    I'm writing a little client using Ruby and Savon. The interface changed significantly from version 0.7 to 0.8.x. All my calls don't work anymore :-(. How can I pass on a local member variable. Please see the example, @userName and @userPassword are not defined within the block. begin @response = @authentication_svc.request :wsdl, "AuthenticateUser" do http.headers["SOAPAction"] = "AuthenticateUser" soap.body = "#{@userName}#{@passwd}" end rescue Savon::SOAP::Fault = e @last_soap_error = e.message end

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  • What is wrong with locking non-static fields? What is the correct way to lock a particular instance?

    - by smartcaveman
    Why is it considered bad practice to lock non-static fields? And, if I am not locking non-static fields, then how do I lock an instance method without locking the method on all other instances of the same or derived class? I wrote an example to make my question more clear. public abstract class BaseClass { private readonly object NonStaticLockObject = new object(); private static readonly object StaticLockObject = new object(); protected void DoThreadSafeAction<T>(Action<T> action) where T: BaseClass { var derived = this as T; if(derived == null) { throw new Exception(); } lock(NonStaticLockObject) { action(derived); } } } public class DerivedClass :BaseClass { private readonly Queue<object> _queue; public void Enqueue(object obj) { DoThreadSafeAction<DerivedClass>(x=>x._queue.Enqueue(obj)); } } If I make the lock on the StaticLockObject, then the DoThreadSafeAction method will be locked for all instances of all classes that derive from BaseClass and that is not what I want. I want to make sure that no other threads can call a method on a particular instance of an object while it is locked.

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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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  • 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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  • 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 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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  • 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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  • 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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  • 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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  • Use variables to decide which object in an array gets an attribute?

    - by DavidR
    I have a web app which has two text areas. When one text area receives a mousedown event, a variable "side" is set, either "left" or "right." When a user selects some text in a text area, three strings are made. One for the text before the beginning of the selection, the selection itself, and the text after the selection to the end. A function is set to return these like this: return { head: head_text, tail: tail_text, sel: sel_text, side: text_side } Now, I have created an array, and I want it to appear in such a way that we get, text.left({"head":"four score", "selection":"and seven", "tail":"years ago."}) I am assuming I would do this by text.side = getSelection(), but how do I get it to evaluate the variable "side" instead of thinking of it as an object within "text"? EDIT: Ok, just to clarify, I might be completely wrong in my ideas in how this works, but here it goes. I want to make it so that a function can look at "text" see within text two objects, "left" and "right," and then evaluate the head, sel, and tail of each object. Would it be easier for me to use two objects?

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