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  • How to implement an interface member that returns void in F#

    - by Drew Noakes
    Imagine the following interface in C#: interface IFoo { void Bar(); } How can I implement this in F#? All the examples I've found during 30 minutes of searching online show only examples that have return types which I suppose is more common in a functional style, but something I can't avoid in this instance. Here's what I have so far: type Bar() = interface IFoo with member this.Bar = void Fails with FS0010: Unexpected keyword 'void' in expression.

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  • Copy all current system data content in memory

    - by Tom Brito
    I'm studying security, and I would like to know: in Windows or Unix based OS environment, is there a way for a malicious program to copy all the content of the computer's memory? My worry is about a program that can get my decrypted data loaded in memory. And how to avoid it.

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  • C# monkey patching - is it possible?

    - by Adal
    Is it possible to write a C# assembly which when loaded will inject a method into a class from another assembly? If yes, will the injected method be available from languages using DLR, like IronPython? namespace IronPython.Runtime { public class Bytes : IList<byte>, ICodeFormattable, IExpressionSerializable { internal byte[] _bytes; //I WANT TO INJECT THIS METHOD public byte[] getbytes() { return _bytes; } } } I need that method, and I would like to avoid recompiling IronPython if possible.

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  • Database model for saving random boolean expressions

    - by zarko.susnjar
    I have expressions like this: (cat OR cats OR kitten OR kitty) AND (dog OR dogs) NOT (pigeon OR firefly) Anyone having idea how to make tables to save those? Before I got request for usage of brackets, I limited usage of operators to avoid ambiguous situations. So only ANDs and NOTs or only ORs and saved those in this manner: operators id | name 1 | AND 2 | OR 3 | NOT keywords id | keyword 1 | cat 2 | dog 3 | firefly expressions id | operator | keywordId 1 | 0 | 1 1 | 1 | 2 1 | 3 | 3 which was: cat AND dog NOT firefly But now, I'm really puzzled...

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  • Optimizing tasks to reduce CPU in a trading application

    - by Joel
    Hello, I have designed a trading application that handles customers stocks investment portfolio. I am using two datastore kinds: Stocks - Contains unique stock name and its daily percent change. UserTransactions - Contains information regarding a specific purchase of a stock made by a user : the value of the purchase along with a reference to Stock for the current purchase. db.Model python modules: class Stocks (db.Model): stockname = db.StringProperty(multiline=True) dailyPercentChange=db.FloatProperty(default=1.0) class UserTransactions (db.Model): buyer = db.UserProperty() value=db.FloatProperty() stockref = db.ReferenceProperty(Stocks) Once an hour I need to update the database: update the daily percent change in Stocks and then update the value of all entities in UserTransactions that refer to that stock. The following python module iterates over all the stocks, update the dailyPercentChange property, and invoke a task to go over all UserTransactions entities which refer to the stock and update their value: Stocks.py # Iterate over all stocks in datastore for stock in Stocks.all(): # update daily percent change in datastore db.run_in_transaction(updateStockTxn, stock.key()) # create a task to update all user transactions entities referring to this stock taskqueue.add(url='/task', params={'stock_key': str(stock.key(), 'value' : self.request.get ('some_val_for_stock') }) def updateStockTxn(stock_key): #fetch the stock again - necessary to avoid concurrency updates stock = db.get(stock_key) stock.dailyPercentChange= data.get('some_val_for_stock') # I get this value from outside ... some more calculations here ... stock.put() Task.py (/task) # Amount of transaction per task amountPerCall=10 stock=db.get(self.request.get("stock_key")) # Get all user transactions which point to current stock user_transaction_query=stock.usertransactions_set cursor=self.request.get("cursor") if cursor: user_transaction_query.with_cursor(cursor) # Spawn another task if more than 10 transactions are in datastore transactions = user_transaction_query.fetch(amountPerCall) if len(transactions)==amountPerCall: taskqueue.add(url='/task', params={'stock_key': str(stock.key(), 'value' : self.request.get ('some_val_for_stock'), 'cursor': user_transaction_query.cursor() }) # Iterate over all transaction pointing to stock and update their value for transaction in transactions: db.run_in_transaction(updateUserTransactionTxn, transaction.key()) def updateUserTransactionTxn(transaction_key): #fetch the transaction again - necessary to avoid concurrency updates transaction = db.get(transaction_key) transaction.value= transaction.value* self.request.get ('some_val_for_stock') db.put(transaction) The problem: Currently the system works great, but the problem is that it is not scaling well… I have around 100 Stocks with 300 User Transactions, and I run the update every hour. In the dashboard, I see that the task.py takes around 65% of the CPU (Stock.py takes around 20%-30%) and I am using almost all of the 6.5 free CPU hours given to me by app engine. I have no problem to enable billing and pay for additional CPU, but the problem is the scaling of the system… Using 6.5 CPU hours for 100 stocks is very poor. I was wondering, given the requirements of the system as mentioned above, if there is a better and more efficient implementation (or just a small change that can help with the current implemntation) than the one presented here. Thanks!! Joel

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  • CakePHP: Can I ignore a field when reading the Model from the DB?

    - by Daniel Magliola
    In one of my models, I have a "LONGTEXT" field that has a big dump of a bunch of stuff that I never care to read, and it slows things down, since I'm moving much more data between the DB and the web app. Is there a way to specify in the model that I want CakePHP to simply ignore that field, and never read it or do anything with it? I really want to avoid the hassle of creating a separate table and a separate model, only for this field. Thanks! Daniel

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  • How do I detect unicode characters in a Java string to resolve sax parser exception

    - by Madhumita
    Suppose I have a string that contains '¿'. How would I find all those unicode characters? Should I test for their code? How would I do that? I want to detect it to avoid sax parser exception which I am getting it while parsing the xml saved as a clob in oracle 10g database. Exception javax.servlet.ServletException: org.xml.sax.SAXParseException: Invalid byte 1 of 1-byte UTF-8 sequence.

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  • How to retrieve caller context object in Ruby ?

    - by David
    Hi, hereafter is my piece of code that I want to simplify in order to avoid passing an extra argument on each call : module M def do_something(context) puts "Called from #{context}" end module_function :do_something end class Foo def do_stuff M.do_something(self) end end Foo.new.do_stuff Is there a way to do the same think without passing 'self' as an input argument to 'do_something' method like this ? module M def do_something puts "Called from #{method that returns caller object}" end module_function :do_something end class Foo def do_stuff M.do_something end end Foo.new.do_stuff Thanks for your support!

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  • c:forEach.items getting repetitively called

    - by Joshua
    Environment: Seam, Richfaces The following code snippet causes the method getUsers to be called multiple times, how do I avoid this in my application so that it gets called only once. <c:forEach items="#{userHome.getUsers()}" var="_user"> </c:forEach>

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  • Visual studio 2010 Errors out on starting "-832" is not a valid value for property "width"

    - by Solmead
    My Visual Studio 2010 was working fine this morning (I run in in XP sP3 under Paralles) I restarted the entire laptop and I started getting this error. I even uninstalled VS2010, deleted the Visual Studio 20010 directory on the My Documents area and reinstalled it, and it is still giving me that error every time I try to start it. I'm not sure if stackoverflow is the place to ask it, but I am at my wits end trying to get this running again (trying to avoid rebuilding the entire Virtual PC) Does anyone know how to fix this?

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  • Retrieving the URL in Django template language

    - by Vernon
    In a Django template, how could I refer to the URL. I want to use it in static pages, to avoid having live links to the current page. Is there a way to do this with the Django template language or do I have to use JavaScript to do it? I would like to do something like {% if current_url == "/about/" %} About {% else %} <a href='/about/'>About</a> {% endif %} I'm using it for a simple blog, so there are no views written for those pages.

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  • Common programming mistakes in .Net when handling exceptions?

    - by Jared Coleson
    What are some of the most common mistakes you've seen made when handling exceptions? It seems like exception handling can be one of the hardest things to learn how to do "right" in .Net. Especially considering the currently #1 ranked answer to Common programming mistakes for .NET developers to avoid? is related to exception handling. Hopefully by listing some of the most common mistakes we can all learn to handle exceptions better.

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  • How to inherit constructors with arguments in .NET?

    - by Soumya92
    I have a "MustInherit" .NET class which declares a constructor with an integer parameter. However, Visual Studio gives me an error when I create any derived class stating that there is no constructor that can be called without any arguments. Is it possible to inherit the constructor with arguments? Right now, I have to use Public Sub New(ByVal A As Integer) MyBase.New(A) End Sub in the derived classes. Is there any way to avoid this?

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  • When should I use $ (and can it always be replaced with parentheses)?

    - by J Cooper
    From what I'm reading, $ is described as "applies a function to its arguments." However, it doesn't seem to work quite like (apply ...) in Lisp, because it's a binary operator, so really the only thing it looks like it does is help to avoid parentheses sometimes, like foo $ bar quux instead of foo (bar quux). Am I understanding it right? Is the latter form considered "bad style"?

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  • How to safely use VSS when using a working directory on a thumb drive?

    - by MatthewMartin
    I know putting code into VSS in general is as safe as putting money into a mutual fund run by Bernard Madoff, but I don't have the luxury of ditching it for subversion. That said, I need to be able to write code on two machines, I'm considering checking out code to a flash thumb drive. Anyone know in advance what I should/shouldn't do to avoid loss of work? Do I need to ensure the drive letter stays the same?

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  • Why does std queue not define a swap method specialisation

    - by Jamie Cook
    I've read that all stl containers provide a specialisation of the swap algorithm so as to avoid calling the copy constructor and two assignment operations that the default method uses. However, when I thought it would be nice to use a queue in some code I was working on I noticed that (unlike vector and deque) queue doesn't provide this method? I just decided to use a deque instead of a queue, but still I'm interested to know why this is?

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  • Why am I getting tree conflicts in subversion?

    - by Greg
    I had a feature branch of my trunk and was merging changes from my trunk into my branch periodically and everything was working fine. Today I went to merge the branch back down into the trunk and any of the files that were added to my trunk after the creation of my branch were flagged as a "tree conflict". Is there any way to avoid this in the future? I don't think these are being properly flagged. Thanks.

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  • Clean checkout from TFS 2008

    - by Luis Medel
    Hi all, I want to pass a project to a colleague without SCC bindings to avoid accidental changes in my repository. Is it possible to do a clean checkout from a TFS 2008 repo? I'm going crazy finding such an option in VS2008. Thanks in advance.

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  • Possible to split one JAX-WS service across multiple source files?

    - by Rob S.
    Hi everyone, Is it possible to split a web service in to multiple classes and still provide a single path to the web service? I know this isn't possible because of the duplicate url-pattern values. It sort of illustrates where we're wanting to go :) <endpoint name="OneBigService" implementation="SmallImpl1" url-pattern="/OneBigService"/> <endpoint name="OneBigService" implementation="SmallImpl2" url-pattern="/OneBigService"/> Basically, how do avoid having one monolithic @WebService class? Thanks! Rob

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