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  • caching previous return values of procedures in scheme

    - by Brock
    In Chapter 16 of "The Seasoned Schemer", the authors define a recursive procedure "depth", which returns 'pizza nested in n lists, e.g (depth 3) is (((pizza))). They then improve it as "depthM", which caches its return values using set! in the lists Ns and Rs, which together form a lookup-table, so you don't have to recurse all the way down if you reach a return value you've seen before. E.g. If I've already computed (depthM 8), when I later compute (depthM 9), I just lookup the return value of (depthM 8) and cons it onto null, instead of recursing all the way down to (depthM 0). But then they move the Ns and Rs inside the procedure, and initialize them to null with "let". Why doesn't this completely defeat the point of caching the return values? From a bit of experimentation, it appears that the Ns and Rs are being reinitialized on every call to "depthM". Am I misunderstanding their point? I guess my question is really this: Is there a way in Scheme to have lexically-scoped variables preserve their values in between calls to a procedure, like you can do in Perl 5.10 with "state" variables?

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  • Finding cause of memory leaks in large PHP stacks

    - by Mike B
    I have CLI script that runs over several thousand iterations between runs and it appears to have a memory leak. I'm using a tweaked version of Zend Framework with Smarty for view templating and each iteration uses several MB worth of code. The first run immediately uses nearly 8MB of memory (which is fine) but every following run adds about 80kb. My main loop looks like this (very simplified) $users = UsersModel::getUsers(); foreach($users as $user) { $obj = new doSomethingAwesome(); $obj->run($user); $obj = null; unset($obj); } The point is that everything in scope should be unset and the memory freed. My understanding is that PHP runs through its garbage collection process at it's own desire but it does so at the end of functions/methods/scripts. So something must be leaking memory inside doSomethingAwesome() but as I said it is a huge stack of code. Ideally, I would love to find some sort of tool that displayed all my variables no matter the scope at some point during execution. Some sort of symbol-table viewer for php. Does anything like that or any other tools that could help nail down memory leaks in php exist?

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  • Django: get count of ForeignKey item in template?

    - by AP257
    Straightforward question - apologies if it is a duplicate, but I can't find the answer if so. I have a User model and a Submission model, like this: class Submission(models.Model): uploaded_by = models.ForeignKey('User') class User(models.Model): name = models.CharField(max_length=250 ) How can I show the number of Submissions made by each user in the template? I've tried {{ user.submission.count }}, like this: for user in users: {{ user.name }} ({{ user.submission.count }} submissions) but no luck...

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  • Unsigned Integer

    - by viswanathan
    I was curious to know what would happen if i assign a negative value to an unsigned variable. The code will look somewhat like this. unsigned int nVal = 0; nVal = -5; It didnt give me any compiler error. When i ran the nVal was having strange value. Could it be that some 2's complement value gets assigned to nVal.

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  • select all values from a dimension for which there are facts in all other dimensions

    - by ideasculptor
    I've tried to simplify for the purposes of asking this question. Hopefully, this will be comprehensible. Basically, I have a fact table with a time dimension, another dimension, and a hierarchical dimension. For the purposes of the question, let's assume the hierarchical dimension is zip code and state. The other dimension is just descriptive. Let's call it 'customer' Let's assume there are 50 customers. I need to find the set of states for which there is at least one zip code in which EVERY customer has at least one fact row for each day in the time dimension. If a zip code has only 49 customers, I don't care about it. If even one of the 50 customers doesn't have a value for even 1 day in a zip code, I don't care about it. Finally, I also need to know which zip codes qualified the state for selection. Note, there is no requirement that every zip code have a full data set - only that at least one zip code does. I don't mind making multiple queries and doing some processing on the client side. This is a dataset that only needs to be generated once per day and can be cached. I don't even see a particularly clean way to do it with multiple queries short of simply brute-force iteration, and there are a heck of a lot of 'zip codes' in the data set (not actually zip codes, but the there are approximately 100,000 entries in the lower level of the hierarchy and several hundred in the top level, so zipcode-state is a reasonable analogy)

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  • what should I take into consideration when choosing a session implementation?

    - by Satoru.Logic
    Hi, all. Yesterday, my supervisor told me that tmp-file-based session should be THE answer to session implementation, and I should abandon any idea of making sessions persistent. He argues that file-based session is much faster and eaiser to use than other choices like db-based or memcached-based implementations. What he said was really a shock to my past learning experience, so please tell me whether he was wrong and why? Thanks in advance.

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  • What do you use two monitors for when you develop?

    - by Yishai
    Although I have two monitors on my desk, I just find that I don't use the second one very often. I see that often people are extolling the virtues of two (or three) monitors, but I haven't gotten into the groove. It gets me thinking that I may be missing some productivity techniques. So how do you organize your two monitors?

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  • Django - Can you use property as the field in an aggregation function?

    - by orokusaki
    I know the short answer because I tried it. Is there any way to accomplish this though (even if only on account of a hack)? class Ticket(models.Model): account = modelfields.AccountField() uuid = models.CharField(max_length=36, unique=True) created = models.DateTimeField(auto_now_add=True) class Meta: ordering = ['created'] @property def repair_cost(self): # cost is a @property of LineItem(models.Model) return self.lineitem_set.aggregate(models.Sum('cost'))

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  • How do I redirect a user using Apache Rewrite, to the fully qualified domain name?

    - by Mark
    Hi Guys, I'm really new to apache mod_rewrite module. I have a page called http://abc in my company intranet. I want users to be redirected to http://abc.somecompanyname.com whenever they type http://abc to the URL bar. Could someone please provide and example or point me in the right direction. I figure this should be quite an easy question to answer. Thanks everyone for you inputs. -Mark

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  • Spring Security ACL: NotFoundException from JDBCMutableAclService.createAcl

    - by user340202
    Hello, I've been working on this task for too long to abandon the idea of using Spring Security to achieve it, but I wish that the community will provide with some support that will help reduce the regret that I have for choosing Spring Security. Enough ranting and now let's get to the point. I'm trying to create an ACL by using JDBCMutableAclService.createAcl as follows: [code] public void addPermission(IWFArtifact securedObject, Sid recipient, Permission permission, Class clazz) { ObjectIdentity oid = new ObjectIdentityImpl(clazz.getCanonicalName(), securedObject.getId()); this.addPermission(oid, recipient, permission); } @Override @Transactional(propagation = Propagation.REQUIRED, isolation = Isolation.READ_UNCOMMITTED, readOnly = false) public void addPermission(ObjectIdentity oid, Sid recipient, Permission permission) { SpringSecurityUtils.assureThreadLocalAuthSet(); MutableAcl acl; try { acl = this.mutableAclService.createAcl(oid); } catch (AlreadyExistsException e) { acl = (MutableAcl) this.mutableAclService.readAclById(oid); } // try { // acl = (MutableAcl) this.mutableAclService.readAclById(oid); // } catch (NotFoundException nfe) { // acl = this.mutableAclService.createAcl(oid); // } acl.insertAce(acl.getEntries().length, permission, recipient, true); this.mutableAclService.updateAcl(acl); } [/code] The call throws a NotFoundException from the line: [code] // Retrieve the ACL via superclass (ensures cache registration, proper retrieval etc) Acl acl = readAclById(objectIdentity); [/code] I believe this is caused by something related to Transactional, and that's why I have tested with many TransactionDefinition attributes. I have also doubted the annotation and tried with declarative transaction definition, but still with no luck. One important point is that I have used the statement used to insert the oid in the database earlier in the method directly on the database and it worked, and also threw a unique constraint exception at me when it tried to insert it in the method. I'm using Spring Security 2.0.8 and IceFaces 1.8 (which doesn't support spring 3.0 but definetely supprorts 2.0.x, specially when I keep caling SpringSecurityUtils.assureThreadLocalAuthSet()). My AppServer is Tomcat 6.0, and my DB Server is MySQL 6.0 I wish to get back a reply soon because I need to get this task off my way

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  • How do I remove/delete/expire a cookie immediately?

    - by dsimard
    I want to remove a cookie I set. If I do this by giving it a expiration date sometime in the past it gets marked as "expires: at end of session". I've noticed that other sites manage to delete the cookie immediately somehow. For example when you logout here on stackoverflow the "user" cookie disappears right away. How?

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  • How do I add code automatically to a derived function in C++

    - by Ian
    I have code that's meant to manage operations on both a networked client and a server, since there is significant overlap between the two. However, there are a few functions here and there that are meant to be exclusively called by the client or server, and accidentally calling a client function on the server (or vice versa) is a significant source of bugs. To reduce these sorts of programming errors, I'm trying to tag functions so that they'll raise a ruckus if they're misused. My current solution is a simple macro at the start of each function that calls an assert if the client or server accesses members they shouldn't. However, this runs into problems when there are multiple derived instances of classes, in that I have to tag the implementation as client or server side in EVERY child class. What I'd like to be able to do is put a tag in the virtual member's signature in the base class, so that I only have to tag it once and not run into errors by forgetting to do it repeatedly. I've considered putting a check in a base class implementation and then referring to it with something like base::functionName, but that runs into the same issue as far as needing to manually add the function call to every implementation. Ideally, I'd be able to have parent versions of the function called automatically like default constructors do. Does anybody know how to achieve something like this in C++? Is there an alternate approach I should be considering? Thanks!

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  • Run a form in another thread

    - by Smith
    i have five forms in my c# project. one host an httplistener that i want to run continionsly. when the listener gets a message, it passes it to a static class, which in turn calls the appropriate forms for another processing. is it possible that the static class calls the new form in a new thread? if so please help me out

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  • Creation of Objects: Constructors or Static Factory Methods

    - by Rachel
    I am going through Effective Java and some of my things which I consider as standard are not suggested by the book, for instance creation of object, I was under the impression that constructors are the best way of doing it and books says we should make use of static factory methods, I am not able to few some advantages and so disadvantages and so am asking this question, here are the benefits of using it. Advantages: One advantage of static factory methods is that, unlike constructors, they have names. A second advantage of static factory methods is that, unlike constructors, they are not required to create a new object each time they’re invoked. A third advantage of static factory methods is that, unlike constructors, they can return an object of any subtype of their return type. A fourth advantage of static factory methods is that they reduce the verbosity of creating parameterized type instances. I am not able to understand this advantage and would appreciate if someone can explain this point Disadvantages: The main disadvantage of providing only static factory methods is that classes without public or protected constructors cannot be subclassed. A second disadvantage of static factory methods is that they are not readily distinguishable from other static methods.I am not getting this point and so would really appreciate some explanation. Reference: Effective Java, Joshua Bloch, Edition 2, pg: 5-10 Also, How to decide to use whether to go for Constructor or Static Factory Method for Object Creation ?

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  • jsf, richfaces, popup window

    - by Hubidubi
    Hi I would like to make a list-detail view with richfaces. There will be a link for every record in the list that should open a new window containing record details. I tried to implement the link this way: <a4j:commandLink oncomplete="window.open('/pages/serviceDetail.jsf','popupWindow', 'dependent=yes, menubar=no, toolbar=no, height=500, width=400')" actionListener="#{monitoringBean.recordDetail}" value="details" /> I use <a4j:keepAlive beanName="monitoringBean" ajaxOnly="false" /> for both the list and the detail page. recordDetail method fills the data of the selected record to a variable of the bean that I would like to display on the detail page. The problem is that keepalive doesn't work, so I get new bean instance on the detail page every time. So the the previously selected record from the other bean is not accessible here. Is there a way to pass parameter (id) to the detail page to handle record selection. Or is there any way to make keepalive work? (I this this would be the easiest). Thanks

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  • jquery and mobile browser compatiblity?

    - by fractalbit
    I want to build a relatively simple version of my site for mobile phones but i will definately need javascript and jquery for many functions. Googling didn't help to find an answer. How is compatibility of jquery with popular browsers in mobile phones? I am talking for smartphones. For example the deafult browsers for these platforms Windows mobile 6+ Android 1.5+ iphone 3g and let's add opera mobile. Has anyone tried it?

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  • Unable to access any widgets in an window.

    - by PP
    I have one GtkWindow with one GtkVBox and GtkEntry. Some times it happens that i am unable to access buttons Buttons, lists, entries. But i am able to add widgets to GtkVBox and it gets updated with new widgets too. Looks like it loses Focus. i tries with setting focus but it does not helps. What might be wrong.

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  • Applescript: Get directory dropped on

    - by Daniel
    Hi, I have a applescript with the following: on open dir tell application "Finder" tell application "Terminal" activate tell application "Terminal" do script "cd " & dir end tell end tell end tell end open It works, and gets the directory thats dropped on it, but it cd's into cd Macintosh HD:Users:USER:Desktop:C Files: Is there any way to replace : with / ? in applescript?

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