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  • UINavigationController: How do I delete a view of a stack

    - by Harry Pham
    Let say here is my stack layout View3 --> Top of the stack View2 View1 HomeView --> Bottom of the stack So I am in View3 now, if I click the Home button, I want to load HomeView, meaning that I need to pop View3, View2, and View1. But if I pop View3, View2 will be displayed. I dont want that. I want View3, View2, and View1 be removed, and HomeView will be displayed. Any idea how?

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  • How to hide zero values in bar3 plot in MATLAB

    - by Doresoom
    I've got a 2-D histogram (the plot is 3D - several histograms graphed side by side) that I've generated with the bar3 plot command. However, all the zero values show up as flat squares in the x-y plane. Is there a way I can prevent MATLAB from displaying the values? I already tried replacing all zeros with NaNs, but it didn't change anything about the plot. Here's the code I've been experimenting with: x1=normrnd(50,15,100,1); %generate random data to test code x2=normrnd(40,13,100,1); x3=normrnd(65,12,100,1); low=min([x1;x2;x3]); high=max([x1;x2;x3]); y=linspace(low,high,(high-low)/4); %establish consistent bins for histogram z1=hist(x1,y); z2=hist(x2,y); z3=hist(x3,y); z=[z1;z2;z3]'; bar3(z) As you can see, there are quite a few zero values on the plot. Closing the figure and re-plotting after replacing zeros with NaNs seems to change nothing: close z(z==0)=NaN; bar3(z)

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  • Cursor returns zero rows from query to table

    - by brockoli
    I've created an SQLiteDatabase in my app and populated it with some data. I can connect to my AVD with a terminal and when I issue select * from articles; I get a list of all the rows in my table and everything looks fine. However, in my code when I query my table, I get a cursor back that has my tables columns, but zero rows of data. Here is my code.. mDbHelper.open(); Cursor articles = mDbHelper.fetchAllArticles(); startManagingCursor(articles); Cursor feeds = mDbHelper.fetchAllFeeds(); startManagingCursor(feeds); mDbHelper.close(); int titleColumn = articles.getColumnIndex("title"); int feedIdColumn = articles.getColumnIndex("feed_id"); int feedTitleColumn = feeds.getColumnIndex("title"); /* Check if our result was valid. */ if (articles != null) { int count = articles.getCount(); /* Check if at least one Result was returned. */ if (articles.moveToFirst()) { In the above code, my Cursor articles returns with my 4 columns, but when I call getCount() it returns zero, even though I can see hundreds of rows of data in that table from command line. Any idea what I might be doing wrong here? Also.. here is my code for fetchAllArticles.. public Cursor fetchAllArticles() { return mDb.query(ARTICLES_TABLE, new String[] {ARTICLE_KEY_ROWID, ARTICLE_KEY_FEED_ID, ARTICLE_KEY_TITLE, ARTICLE_KEY_URL}, null, null, null, null, null); } Rob W.

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  • finding N contiguous zero bits in an integer to the left of the MSB from another

    - by James Morris
    First we find the MSB of the first integer, and then try to find a region of N contiguous zero bits within the second number which is to the left of the MSB from the first integer. Here is the C code for my solution: typedef unsigned int t; unsigned const t_bits = sizeof(t) * CHAR_BIT; _Bool test_fit_within_left_of_msb( unsigned width, t val1, t val2, unsigned* offset_result) { unsigned offbit = 0; unsigned msb = 0; t mask; t b; while(val1 >>= 1) ++msb; while(offbit + width < t_bits - msb) { mask = (((t)1 << width) - 1) << (t_bits - width - offbit); b = val2 & mask; if (!b) { *offset_result = offbit; return true; } if (offbit++) /* this conditional bothers me! */ b <<= offbit - 1; while(b <<= 1) offbit++; } return false; } Aside from faster ways of finding the MSB of the first integer, the commented test for a zero offbit seems a bit extraneous, but necessary to skip the highest bit of type t if it is set. I have also implemented similar algorithms but working to the right of the MSB of the first number, so they don't require this seemingly extra condition. How can I get rid of this extra condition, or even, are there far more optimal solutions?

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  • Service Stack

    - by csharp-source.net
    ServiceStack allows you to build re-usable SOA-style web services with plain POCO DataContract classes. The same DTO's can be shared with a .NET client application eliminating the need for any generated code. With no configuration required, web services created are immediately discoverable and callable via the following supported endpoints: - REST and XML - REST and JSON - SOAP 1.1 / 1.2 Services can run on both Mono and the .NET Framework and be hosted in either a ASP.NET Web Application, a Windows Service or Console application.

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  • LEMP Stack on Ubuntu Server 13.04 not parsing PHP Switch Statement Properly

    - by schester
    On my Ubuntu 12.04 Server LTS on nginx 1.1.19, the following PHP code works properly: switch($_SESSION['user']['permissions']) { case 9: echo "Super Admin Privileges"; break; case 0: echo "Operator Privileges"; break; case 1: echo "Line Leader Privileges"; break; case 2: echo "Supervisor Privileges"; break; case 3: echo "Engineer Privileges"; break; case 4: echo "Manager Privileges"; break; case 5: echo "Administrator Privileges"; break; default: echo "Operator Privileges"; } However, I have a backup server running Ubuntu Server 13.04 on nginx 1.4.1 which has the exact same copy of the script (synced) but instead of breaking on the break; command, it echos the whole php script. The output on the 12.04 Box is similar to this: You are logged in with Super Admin Privileges But on the 13.04 Box, the output is like this: You are logged in logged in with Super Admin Privileges"; break; case 0: echo "Operator Privileges"; break; case 1: echo "Line Leader Privileges"; break; case 2: echo "Supervisor Privileges"; break; case 3: echo "Engineer Privileges"; break; case 4: echo "Manager Privileges"; break; case 5: echo "Administrator Privileges"; break; default: echo "Operator Privileges"; } ?> I have also tried changing the script from switch statement to if statements but same results. Any idea what is wrong?

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  • The C++ web stack, is there one?

    - by NimChimpsky
    Java would be jsps and servlets (or a framework such as Spring) running on the JVM and tomcat (or glassfish etc). C# would be asp and C# running on dot.net framework and IIS ? (I have no experience with this please correct and improve my terminology) Is there an equivalent for C++ ? I could happily call some C++ from a java servlet/controller but was wondering if there are existing frameworks and libraries out there specifically for creating business logic in C++ with a web front end.

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  • CVE-2012-3410 stack-based buffer overflow vulnerability in Bash

    - by RitwikGhoshal
    CVE DescriptionCVSSv2 Base ScoreComponentProduct and Resolution CVE-2012-3410 Buffer overflow vulnerability 4.6 Bash Solaris 11 Contact Support Solaris 10 SPARC: 126546-04 X86: 126547-04 Solaris 9 Contact Support This notification describes vulnerabilities fixed in third-party components that are included in Oracle's product distributions.Information about vulnerabilities affecting Oracle products can be found on Oracle Critical Patch Updates and Security Alerts page.

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  • the web technology stack is too deep [closed]

    - by AgostinoX
    A standard state-of-the-art project requires at least jsf + spring + faces palette + orm. That's a lot of stuff. Also frameworks like spring misses to bring to the point of starting developing. Otherwise, things like spring-roo wuoldn't even exist. The solution to this may be buy support. Have dedicated people doing integration. Switch to ruby on rails. Switch to dot.net. Since this is a problem, I'm intrested in HOW people address this (java ee) specific concern.

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  • The Simplicity of the Oracle Stack

    - by user801960
    For many retailers, technology is something they know they need to optimise business operations, but do they really understand it and how can they select the solutions they need from the many vendors on the market? Retail is a data heavy industry, with the average retailer managing thousands of SKUs and hundreds of categories through multiple channels. Add to this the exponential growth in data driven by social media and mobile activities, and the process can seem overwhelming. Handling data of this magnitude and analyzing it effectively to gain actionable insight is a huge task, and needs several IT components to work together harmoniously to make the best use of the data available and make smarter decisions. With this in mind, Oracle has produced a video to make it easier for businesses to understand its global data IT solutions and how they integrate seamlessly with Oracle’s other solutions to enable organisations to operate as effectively as possible. The video uses an orchestra as an analogy for IT solutions and clever illustration to demonstrate the value of the Oracle brand. This video can be viewed at http://medianetwork.oracle.com/video/player/1622148401001. To find out more about how Oracle’s products and services can help retailers to deliver better results, visit the Oracle Retail website.

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  • vagrant fails to bring up additional adapter for centos vm using virtual box provider

    - by Anadi Misra
    this is in continuation of the question asked here about host only adapter on dhcp I upgraded to vagrant 1.6.3 and the updated Vagrantfile to following setting for multiple adapters # add additional adapter for inter machine networking dev.vm.network :private_network, :type => "dhcp", :adapter => "2", :netmask => "255.255.255.0" it goes through creating adapters but then fails bringing up the mic on vm Anadis-MacBook-Pro:full-stack-env anadi$ vagrant up Bringing machine 'full-stack-env' up with 'virtualbox' provider... ==> full-stack-env: Clearing any previously set forwarded ports... ==> full-stack-env: Clearing any previously set network interfaces... ==> full-stack-env: Preparing network interfaces based on configuration... full-stack-env: Adapter 1: nat full-stack-env: Adapter 2: hostonly ==> full-stack-env: Forwarding ports... full-stack-env: 22 => 4223 (adapter 1) full-stack-env: 8080 => 8090 (adapter 1) ==> full-stack-env: Running 'pre-boot' VM customizations... ==> full-stack-env: Booting VM... ==> full-stack-env: Waiting for machine to boot. This may take a few minutes... full-stack-env: SSH address: 127.0.0.1:4223 full-stack-env: SSH username: vagrant full-stack-env: SSH auth method: private key full-stack-env: Warning: Connection timeout. Retrying... full-stack-env: Warning: Connection timeout. Retrying... full-stack-env: Warning: Remote connection disconnect. Retrying... ==> full-stack-env: Machine booted and ready! ==> full-stack-env: Checking for guest additions in VM... ==> full-stack-env: Setting hostname... ==> full-stack-env: Configuring and enabling network interfaces... The following SSH command responded with a non-zero exit status. Vagrant assumes that this means the command failed! ARPCHECK=no /sbin/ifup eth 2> /dev/null Stdout from the command: Device eth does not seem to be present, delaying initialization. Stderr from the command: how ever when I log in to the environment I see two network interfaces as expected Anadis-MacBook-Pro:full-stack-env anadi$ vagrant ssh Last login: Wed Jun 4 12:54:47 2014 from 10.0.2.2 [vagrant@full-stack-env ~]$ ifconfig eth0 Link encap:Ethernet HWaddr 08:00:27:BD:39:57 inet addr:10.0.2.15 Bcast:10.0.2.255 Mask:255.255.255.0 inet6 addr: fe80::a00:27ff:febd:3957/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:511 errors:0 dropped:0 overruns:0 frame:0 TX packets:360 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:54574 (53.2 KiB) TX bytes:46675 (45.5 KiB) eth1 Link encap:Ethernet HWaddr 08:00:27:A3:86:C9 inet addr:172.28.128.3 Bcast:172.28.128.255 Mask:255.255.255.0 inet6 addr: fe80::a00:27ff:fea3:86c9/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:5 errors:0 dropped:0 overruns:0 frame:0 TX packets:9 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:1360 (1.3 KiB) TX bytes:894 (894.0 b) lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 inet6 addr: ::1/128 Scope:Host UP LOOPBACK RUNNING MTU:16436 Metric:1 RX packets:0 errors:0 dropped:0 overruns:0 frame:0 TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:0 (0.0 b) TX bytes:0 (0.0 b) I am bit confused here on why it is trying to add another mic (eth2)? In the VM I used for creating this vagrant box, I had added two NICs already.

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  • Design by Contract with Microsoft .Net Code Contract

    - by Fredrik N
    I have done some talks on different events and summits about Defensive Programming and Design by Contract, last time was at Cornerstone’s Developer Summit 2010. Next time will be at SweNug (Sweden .Net User Group). I decided to write a blog post about of some stuffs I was talking about. Users are a terrible thing! Protect your self from them ”Human users have a gift for doing the worst possible thing at the worst possible time.” – Michael T. Nygard, Release It! The kind of users Michael T. Nygard are talking about is the users of a system. We also have users that uses our code, the users I’m going to focus on is the users of our code. Me and you and another developers. “Any fool can write code that a computer can understand. Good programmers write code that humans can understand.” – Martin Fowler Good programmers also writes code that humans know how to use, good programmers also make sure software behave in a predictable manner despise inputs or user actions. Design by Contract   Design by Contract (DbC) is a way for us to make a contract between us (the code writer) and the users of our code. It’s about “If you give me this, I promise to give you this”. It’s not about business validations, that is something completely different that should be part of the domain model. DbC is to make sure the users of our code uses it in a correct way, and that we can rely on the contract and write code in a way where we know that the users will follow the contract. It will make it much easier for us to write code with a contract specified. Something like the following code is something we may see often: public void DoSomething(Object value) { value.DoIKnowThatICanDoThis(); } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } Where “value” can be uses directly or passed to other methods and later be used. What some of us can easily forget here is that the “value” can be “null”. We will probably not passing a null value, but someone else that uses our code maybe will do it. I think most of you (including me) have passed “null” into a method because you don’t know if the argument need to be specified to a valid value etc. I bet most of you also have got the “Null reference exception”. Sometimes this “Null reference exception” can be hard and take time to fix, because we need to search among our code to see where the “null” value was passed in etc. Wouldn’t it be much better if we can as early as possible specify that the value can’t not be null, so the users of our code also know it when the users starts to use our code, and before run time execution of the code? This is where DbC comes into the picture. We can use DbC to specify what we need, and by doing so we can rely on the contract when we write our code. So the code above can actually use the DoIKnowThatICanDoThis() method on the value object without being worried that the “value” can be null. The contract between the users of the code and us writing the code, says that the “value” can’t be null.   Pre- and Postconditions   When working with DbC we are specifying pre- and postconditions.  Precondition is a condition that should be met before a query or command is executed. An example of a precondition is: “The Value argument of the method can’t be null”, and we make sure the “value” isn’t null before the method is called. Postcondition is a condition that should be met when a command or query is completed, a postcondition will make sure the result is correct. An example of a postconditon is “The method will return a list with at least 1 item”. Commands an Quires When using DbC, we need to know what a Command and a Query is, because some principles that can be good to follow are based on commands and queries. A Command is something that will not return anything, like the SQL’s CREATE, UPDATE and DELETE. There are two kinds of Commands when using DbC, the Creation commands (for example a Constructor), and Others. Others can for example be a Command to add a value to a list, remove or update a value etc. //Creation commands public Stack(int size) //Other commands public void Push(object value); public void Remove(); .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }   A Query, is something that will return something, for example an Attribute, Property or a Function, like the SQL’s SELECT.   There are two kinds of Queries, the Basic Queries  (Quires that aren’t based on another queries), and the Derived Queries, queries that is based on another queries. Here is an example of queries of a Stack: //Basic Queries public int Count; public object this[int index] { get; } //Derived Queries //Is related to Count Query public bool IsEmpty() { return Count == 0; } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } To understand about some principles that are good to follow when using DbC, we need to know about the Commands and different Queries. The 6 Principles When working with DbC, it’s advisable to follow some principles to make it easier to define and use contracts. The following DbC principles are: Separate commands and queries. Separate basic queries from derived queries. For each derived query, write a postcondition that specifies what result will be returned, in terms of one or more basic queries. For each command, write a postcondition that specifies the value of every basic query. For every query and command, decide on a suitable precondition. Write invariants to define unchanging properties of objects. Before I will write about each of them I want you to now that I’m going to use .Net 4.0 Code Contract. I will in the rest of the post uses a simple Stack (Yes I know, .Net already have a Stack class) to give you the basic understanding about using DbC. A Stack is a data structure where the first item in, will be the first item out. Here is a basic implementation of a Stack where not contract is specified yet: public class Stack { private object[] _array; //Basic Queries public uint Count; public object this[uint index] { get { return _array[index]; } set { _array[index] = value; } } //Derived Queries //Is related to Count Query public bool IsEmpty() { return Count == 0; } //Is related to Count and this[] Query public object Top() { return this[Count]; } //Creation commands public Stack(uint size) { Count = 0; _array = new object[size]; } //Other commands public void Push(object value) { this[++Count] = value; } public void Remove() { this[Count] = null; Count--; } } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }   Note: The Stack is implemented in a way to demonstrate the use of Code Contract in a simple way, the implementation may not look like how you would implement it, so don’t think this is the perfect Stack implementation, only used for demonstration.   Before I will go deeper into the principles I will simply mention how we can use the .Net Code Contract. I mention before about pre- and postcondition, is about “Require” something and to “Ensure” something. When using Code Contract, we will use a static class called “Contract” and is located in he “System.Diagnostics.Contracts” namespace. The contract must be specified at the top or our member statement block. To specify a precondition with Code Contract we uses the Contract.Requires method, and to specify a postcondition, we uses the Contract.Ensure method. Here is an example where both a pre- and postcondition are used: public object Top() { Contract.Requires(Count > 0, "Stack is empty"); Contract.Ensures(Contract.Result<object>() == this[Count]); return this[Count]; } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }   The contract above requires that the Count is greater than 0, if not we can’t get the item at the Top of a Stack. We also Ensures that the results (By using the Contract.Result method, we can specify a postcondition that will check if the value returned from a method is correct) of the Top query is equal to this[Count].   1. Separate Commands and Queries   When working with DbC, it’s important to separate Command and Quires. A method should either be a command that performs an Action, or returning information to the caller, not both. By asking a question the answer shouldn’t be changed. The following is an example of a Command and a Query of a Stack: public void Push(object value) public object Top() .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }   The Push is a command and will not return anything, just add a value to the Stack, the Top is a query to get the item at the top of the stack.   2. Separate basic queries from derived queries There are two different kinds of queries,  the basic queries that doesn’t rely on another queries, and derived queries that uses a basic query. The “Separate basic queries from derived queries” principle is about about that derived queries can be specified in terms of basic queries. So this principles is more about recognizing that a query is a derived query or a basic query. It will then make is much easier to follow the other principles. The following code shows a basic query and a derived query: //Basic Queries public uint Count; //Derived Queries //Is related to Count Query public bool IsEmpty() { return Count == 0; } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }   We can see that IsEmpty will use the Count query, and that makes the IsEmpty a Derived query.   3. For each derived query, write a postcondition that specifies what result will be returned, in terms of one or more basic queries.   When the derived query is recognize we can follow the 3ed principle. For each derived query, we can create a postcondition that specifies what result our derived query will return in terms of one or more basic queries. Remember that DbC is about contracts between the users of the code and us writing the code. So we can’t use demand that the users will pass in a valid value, we must also ensure that we will give the users what the users wants, when the user is following our contract. The IsEmpty query of the Stack will use a Count query and that will make the IsEmpty a Derived query, so we should now write a postcondition that specified what results will be returned, in terms of using a basic query and in this case the Count query, //Basic Queries public uint Count; //Derived Queries public bool IsEmpty() { Contract.Ensures(Contract.Result<bool>() == (Count == 0)); return Count == 0; } The Contract.Ensures is used to create a postcondition. The above code will make sure that the results of the IsEmpty (by using the Contract.Result to get the result of the IsEmpty method) is correct, that will say that the IsEmpty will be either true or false based on Count is equal to 0 or not. The postcondition are using a basic query, so the IsEmpty is now following the 3ed principle. We also have another Derived Query, the Top query, it will also need a postcondition and it uses all basic queries. The Result of the Top method must be the same value as the this[] query returns. //Basic Queries public uint Count; public object this[uint index] { get { return _array[index]; } set { _array[index] = value; } } //Derived Queries //Is related to Count and this[] Query public object Top() { Contract.Ensures(Contract.Result<object>() == this[Count]); return this[Count]; } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }   4. For each command, write a postcondition that specifies the value of every basic query.   For each command we will create a postconditon that specifies the value of basic queries. If we look at the Stack implementation we will have three Commands, one Creation command, the Constructor, and two others commands, Push and Remove. Those commands need a postcondition and they should include basic query to follow the 4th principle. //Creation commands public Stack(uint size) { Contract.Ensures(Count == 0); Count = 0; _array = new object[size]; } //Other commands public void Push(object value) { Contract.Ensures(Count == Contract.OldValue<uint>(Count) + 1); Contract.Ensures(this[Count] == value); this[++Count] = value; } public void Remove() { Contract.Ensures(Count == Contract.OldValue<uint>(Count) - 1); this[Count] = null; Count--; } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }   As you can see the Create command will Ensures that Count will be 0 when the Stack is created, when a Stack is created there shouldn’t be any items in the stack. The Push command will take a value and put it into the Stack, when an item is pushed into the Stack, the Count need to be increased to know the number of items added to the Stack, and we must also make sure the item is really added to the Stack. The postconditon of the Push method will make sure the that old value of the Count (by using the Contract.OldValue we can get the value a Query has before the method is called)  plus 1 will be equal to the Count query, this is the way we can ensure that the Push will increase the Count with one. We also make sure the this[] query will now contain the item we pushed into the Stack. The Remove method must make sure the Count is decreased by one when the top item is removed from the Stack. The Commands is now following the 4th principle, where each command now have a postcondition that used the value of basic queries. Note: The principle says every basic Query, the Remove only used one Query the Count, it’s because this command can’t use the this[] query because an item is removed, so the only way to make sure an item is removed is to just use the Count query, so the Remove will still follow the principle.   5. For every query and command, decide on a suitable precondition.   We have now focused only on postcondition, now time for some preconditons. The 5th principle is about deciding a suitable preconditon for every query and command. If we starts to look at one of our basic queries (will not go through all Queries and commands here, just some of them) the this[] query, we can’t pass an index that is lower then 1 (.Net arrays and list are zero based, but not the stack in this blog post ;)) and the index can’t be lesser than the number of items in the stack. So here we will need a preconditon. public object this[uint index] { get { Contract.Requires(index >= 1); Contract.Requires(index <= Count); return _array[index]; } } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } Think about the Contract as an documentation about how to use the code in a correct way, so if the contract could be specified elsewhere (not part of the method body), we could simply write “return _array[index]” and there is no need to check if index is greater or lesser than Count, because that is specified in a “contract”. The implementation of Code Contract, requires that the contract is specified in the code. As a developer I would rather have this contract elsewhere (Like Spec#) or implemented in a way Eiffel uses it as part of the language. Now when we have looked at one Query, we can also look at one command, the Remove command (You can see the whole implementation of the Stack at the end of this blog post, where precondition is added to more queries and commands then what I’m going to show in this section). We can only Remove an item if the Count is greater than 0. So we can write a precondition that will require that Count must be greater than 0. public void Remove() { Contract.Requires(Count > 0); Contract.Ensures(Count == Contract.OldValue<uint>(Count) - 1); this[Count] = null; Count--; } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }   6. Write invariants to define unchanging properties of objects.   The last principle is about making sure the object are feeling great! This is done by using invariants. When using Code Contract we can specify invariants by adding a method with the attribute ContractInvariantMethod, the method must be private or public and can only contains calls to Contract.Invariant. To make sure the Stack feels great, the Stack must have 0 or more items, the Count can’t never be a negative value to make sure each command and queries can be used of the Stack. Here is our invariant for the Stack object: [ContractInvariantMethod] private void ObjectInvariant() { Contract.Invariant(Count >= 0); } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }   Note: The ObjectInvariant method will be called every time after a Query or Commands is called. Here is the full example using Code Contract:   public class Stack { private object[] _array; //Basic Queries public uint Count; public object this[uint index] { get { Contract.Requires(index >= 1); Contract.Requires(index <= Count); return _array[index]; } set { Contract.Requires(index >= 1); Contract.Requires(index <= Count); _array[index] = value; } } //Derived Queries //Is related to Count Query public bool IsEmpty() { Contract.Ensures(Contract.Result<bool>() == (Count == 0)); return Count == 0; } //Is related to Count and this[] Query public object Top() { Contract.Requires(Count > 0, "Stack is empty"); Contract.Ensures(Contract.Result<object>() == this[Count]); return this[Count]; } //Creation commands public Stack(uint size) { Contract.Requires(size > 0); Contract.Ensures(Count == 0); Count = 0; _array = new object[size]; } //Other commands public void Push(object value) { Contract.Requires(value != null); Contract.Ensures(Count == Contract.OldValue<uint>(Count) + 1); Contract.Ensures(this[Count] == value); this[++Count] = value; } public void Remove() { Contract.Requires(Count > 0); Contract.Ensures(Count == Contract.OldValue<uint>(Count) - 1); this[Count] = null; Count--; } [ContractInvariantMethod] private void ObjectInvariant() { Contract.Invariant(Count >= 0); } } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } Summary By using Design By Contract we can make sure the users are using our code in a correct way, and we must also make sure the users will get the expected results when they uses our code. This can be done by specifying contracts. To make it easy to use Design By Contract, some principles may be good to follow like the separation of commands an queries. With .Net 4.0 we can use the Code Contract feature to specify contracts.

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  • x86_64 Assembly Command Line Arguments

    - by Brandon oubiub
    I'm new to assembly, and I just got familiar with the call stack, so bare with me. To get the command line arguments in x86_64 on Mac OS X, I can do the following: _main: sub rsp, 8 ; 16 bit stack alignment mov rax, 0 mov rdi, format mov rsi, [rsp + 32] call _printf Where format is "%s". rsi gets set to argv[0]. So, from this, I drew out what (I think) the stack looks like initially: top of stack <- rsp after alignment return address <- rsp at beginning (aligned rsp + 8) [something] <- rsp + 16 argc <- rsp + 24 argv[0] <- rsp + 32 argv[1] <- rsp + 40 ... ... bottom of stack And so on. Sorry if that's hard to read. I'm wondering what [something] is. After a few tests, I find that it is usually just 0. However, occasionally, it is some (seemingly) random number. EDIT: Also, could you tell me if the rest of my stack drawing is correct?

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  • Complete stack traces from Hyperic

    - by Mike Kushner
    I've setup Hyperic to run on our CI-machine, and every once in a while it reacts to some random stack trace and sends of an alert. So far so good, we've caught a lot of intermittent bugs that way. My only issue is that the alert only contains the first error line and not the entire stack trace, which requires me to access the machine and look at the logs manually. Is there any way to modify the alert message to contain more information, alternatively to include the log file in the alert mail?

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  • How do I recover jegs with zero bytes?

    - by Jill
    I downloaded some wedding photos into my external drive about a month ago. A total of 3 cards were downloaded into 3 different files. The first file lists all of the photos, about 600 images, but they have zero bytes. The other 2 files are fine. I can't recover the compact flash card because I have used it too many times since then. Is there any way to recover the images on my drive?

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  • How do I recover JPEGs with zero bytes?

    - by Jill
    I downloaded some wedding photos into my external drive about a month ago. A total of 3 cards were downloaded into 3 different files. The first file lists all of the photos, about 600 images, but they have zero bytes. The other 2 files are fine. I can't recover the compact flash card because I have used it too many times since then. Is there any way to recover the images on my drive?

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  • Set automatic axis limits without defaulting to zero (Excel)

    - by djeidot
    I am build a bar chart in Excel with data values ranging from e.g. 10 to 20. I want the X axis limits to be automatic, but although the right limit (near 20) works correctly, the left limit always defaults to 0. I'd like the left limit to be near 10, instead of zero, without having to have the limit fixed. Is there any way to do this?

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  • Buffer Overflow (vs) Buffer OverRun (vs) Stack Overflow [closed]

    - by joe
    Possible Duplicate: What is the difference between a stack overflow and buffer overflow ? What is the difference between Buffer Overflow and Buffer Overrun? What is the difference between Buffer Overrun and Stack Overflow? Please include code examples. I have looked at the terms in Wikipedia, but I am unable to match with programming in C or C++ or Java.

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  • Jquery history, inspect the history stack

    - by nickmorss
    Im using this history jquery plugin http://www.mikage.to/jquery/jquery_history.html and im trying to inspect the back stack. I can call this $.historyCurrentHash to return the current hash, but im trying to figure out how to look one step back in the stack. if i try calling this $.historyBackStack, but i just get an 'undefined'. anyone got any ideas? I can see that its not a public variable, but im wondering if i need to modify the library or just call it in a different way

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  • Azure storage: Uploaded files with size zero bytes

    - by Fabio Milheiro
    When I upload an image file to a blob, the image is uploaded apparently successfully (no errors). When I go to cloud storage studio, the file is there, but with a size of 0 (zero) bytes. The following is the code that I am using: // These two methods belong to the ContentService class used to upload // files in the storage. public void SetContent(HttpPostedFileBase file, string filename, bool overwrite) { CloudBlobContainer blobContainer = GetContainer(); var blob = blobContainer.GetBlobReference(filename); if (file != null) { blob.Properties.ContentType = file.ContentType; blob.UploadFromStream(file.InputStream); } else { blob.Properties.ContentType = "application/octet-stream"; blob.UploadByteArray(new byte[1]); } } public string UploadFile(HttpPostedFileBase file, string uploadPath) { if (file.ContentLength == 0) { return null; } string filename; int indexBar = file.FileName.LastIndexOf('\\'); if (indexBar > -1) { filename = DateTime.UtcNow.Ticks + file.FileName.Substring(indexBar + 1); } else { filename = DateTime.UtcNow.Ticks + file.FileName; } ContentService.Instance.SetContent(file, Helper.CombinePath(uploadPath, filename), true); return filename; } // The above code is called by this code. HttpPostedFileBase newFile = Request.Files["newFile"] as HttpPostedFileBase; ContentService service = new ContentService(); blog.Image = service.UploadFile(newFile, string.Format("{0}{1}", Constants.Paths.BlogImages, blog.RowKey)); Before the image file is uploaded to the storage, the Property InputStream from the HttpPostedFileBase appears to be fine (the size of the of image corresponds to what is expected! And no exceptions are thrown). And the really strange thing is that this works perfectly in other cases (uploading Power Points or even other images from the Worker role). The code that calls the SetContent method seems to be exactly the same and file seems to be correct since a new file with zero bytes is created at the correct location. Does any one have any suggestion please? I debugged this code dozens of times and I cannot see the problem. Any suggestions are welcome! Thanks

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