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  • How does make_pair know the types of its args?

    - by bobobobo
    The definition for make_pair in the MSVC++ "utility" header is: template<class _Ty1, class _Ty2> inline pair<_Ty1, _Ty2> make_pair(_Ty1 _Val1, _Ty2 _Val2) { // return pair composed from arguments return (pair<_Ty1, _Ty2>(_Val1, _Val2)); } I use make_pair all the time though without putting the argument types in angle brackets: map<string,int> theMap ; theMap.insert( make_pair( "string", 5 ) ) ; Shouldn't I have to tell make_pair that the first argument is std::string and not char* ? How does it know?

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  • get attribute value from html code in java

    - by sang
    Hi All i have HTML string value and i want to get one attribute(id) value from that html String value can u help me how to do it?? String msHTMLFile = "<ABBR class='HighlightClass' id='highlight40001' style=\"BACKGROUND-COLOR: yellow\" >Fetal/Neonatal Morbidity and Mortality</ABBR>"; result should come - highlight40001;

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  • What is a .NET application domain?

    - by Luke
    In particular, what are the implications of running code in two different application domains? How is data normally passed across the application domain boundary? Is it the same as passing data across the process boundary? I'm curious to know more about this abstraction and what it is useful for. EDIT: Good existing coverage of the AppDomain class in general at http://stackoverflow.com/questions/622516/i-dont-understand-appdomains

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  • saving value selected in a list when submit button is cliked

    - by kawtousse
    Hi everyone, In my JSP I have a dropdownlist and a submit button when clicking the submit button I loose the value already selected in my list. I am using the jstl because i need to construct other table corresponding the value selected in my list.For that I must call a submit button but the problem; it reset the value selected I want to know if there is a way to save the value selected in my list even I click a submit button. I work with JSP and eclipse environment. Think you for your help.

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  • How to get option value (javascript)

    - by Mahmoud
    Below are the options that i have in my code <label id="subn"> <select name="subs" id="subs"> <option value="nothing">Choose a Subject</option> <option value="General Question">General Question</option> <option value="MemberShip Area">MemberShip Area</option> <option value="Others">Others</option> </select> </label> and i want to create a javascript that well check if the user select a subject other than the first below what i tried using if (document.getElementsByTagName('option') == "nothing"){ document.getElementById("subn").innerHTML = "Subject is Required!"; document.getElementById("subs").focus(); return false; }

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  • distinction between using .text and .value in VBA access

    - by every_answer_gets_a_point
    i am passing the textbox1.text values into a query and sometimes into a string sometimes i say this: dim combor1 as string combor1 = comboReason1.Text how do i know when i should put combor1=comboreason1.value ?? also why do i need to set focus for a control to reference its property? that doesn't make sense to me also when i set combor4 = comboReason4.Value and the .value is null, then i get an error about invalid use of null please help!

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  • Only get the value if a condition is true

    - by Autolycus
    I am checking to see if element1, element 2 or element 3 exists and then add them to finalData if they exist. However if one of those dont exist or are not true then I just want to add the elements whose bool value is true! Below is my code bool hasElement1 = ( from Playlist in loaded.Descendants("Node") select Playlist.Descendants("Element1").Any() ).Single(); bool hasElement2 = ( from Playlist in loaded.Descendants("Node") select Playlist.Descendants("Element2").Any() ).Single(); bool hasElement3 = ( from Playlist in loaded.Descendants("Node") select Playlist.Descendants("Element2").Any() ).Single(); var finalData = from x in loaded.Descendants("Node") select new { Element1 = x.Descendants("Element1").First().Value, Element2 = x.Descendants("Element2").First().Value, Element3 = x.Descendants("Element3").First().Value, };

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  • in R, how can i save the value of "print"

    - by alex
    in R , when i use "print", i can see all the values, but how can i save this as a vector for example, in for loop, for (i in 1:10), i want the value of A , when i= 1,2,3,4..... but if i use the x=A, it only have the final value of A which is the value when i = 10. so , how can i save the vaule in print(A)

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  • TSQL to Map User to Database

    - by dtrick
    So I'm not able to user enterprise manager to do this... If I was I wouldn't even be asking this question. So I'm wondering if there is a way through TSQL to execute a command that maps a User to a particular Database and grants them 'owner' permissions. Thanks...

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  • Rails and a development domain

    - by Adam
    I'm trying to use http://ls1.bigseapreview.com as a domain for a Rails project. The problem is it doesn't seem to be correctly mapping any routing apart from the home page. I have added /about but you can see that you will just get a 404, but it works locally. What do I have to do to fix this?

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  • how to place the value for text area

    - by udaya
    Hi while I am performing the edit function .. i have a textarea where i type some text and submit <tr align="left"> <td class="table_label">Reason </td> <td><textarea cols="17" class="text_box_login_14_width_150" size="5" name="txtReason" id="txtReason"></textarea></td> </tr> when i submit i must receive the value in the edit form <td> <textarea id="txtReason" name="txtReason" value="<?= $row['dReason']?>"></textarea> </td> but i dont receive the value for text area how to receive the value

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  • Run PHP code on a specific domain only

    - by curtismchale
    I need to echo out some specific php code only on the sub-domain of a site. This is where I am so far. <?php if($_SERVER['SERVER_NAME'] != "http://support.demo.com") echo "<?php bb_head(); ?>"; ?> Of course if this worked I'd not be asking a question. Help is appreciated.

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  • Changing a site name or domain

    - by halabira
    I got an active social networking site right now with about 530 members and I would like to change my site's domain name to another one.My question is how can you do this efficiently without losing my members?Do I need to create a redirect page for the old members?

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  • What is the answer to this homework about maps and collections? [closed]

    - by Bishan
    Maps collection is referred to an dictionary because of the way it works. Each entry into a maps collection involves a pair of objects. In a maps collection, an object associates the key which determines where the object is stored in the map. The key object in the maps collection can be duplicated. A stack which has Last In First Out storage mechanism can be considered as a maps collection. I think #1,#2,#3 and #5 are Correct in above, but I have doubt with #5. Am I correct?

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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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  • Add Free Google Apps to Your Website or Blog

    - by Matthew Guay
    Would you like to have an email address from your own domain, but prefer Gmail’s interface and integration with Google Docs?  Here’s how you can add the free Google Apps Standard to your site and get the best of both worlds. Note: To signup for Google Apps and get it setup on your domain, you will need to be able to add info to your WordPress blog or change Domain settings manually. Getting Started Head to the Google Apps signup page (link below), and click the Get Started button on the right.  Note that we are signing up for the free Google Apps which allows a max of 50 users; if you need more than 50 email addresses for your domain, you can choose Premiere Edition instead for $50/year. Select that you are the Administrator of the domain, and enter the domain or subdomain you want to use with Google Apps.  Here we’re adding Google Apps to the techinch.com site, but we could instead add Apps to mail.techinch.com if needed…click Get Started. Enter your name, phone number, an existing email address, and other Administrator information.  The Apps signup page also includes some survey questions about your organization, but you only have to fill in the required fields. On the next page, enter a username and password for the administrator account.  Note that the user name will also be the administrative email address as [email protected]. Now you’re ready to authenticate your Google Apps account with your domain.  The steps are slightly different depending on whether your site is on WordPress.com or on your own hosting service or server, so we’ll show how to do it both ways.   Authenticate and Integrate Google Apps with WordPress.com To add Google Apps to a domain you have linked to your WordPress.com blog, select Change yourdomain.com CNAME record and click Continue. Copy the code under #2, which should be something like googleabcdefg123456.  Do not click the button at the bottom; wait until we’ve completed the next step.   Now, in a separate browser window or tab, open your WordPress Dashboard.  Click the arrow beside Upgrades, and select Domains from the menu. Click the Edit DNS link beside the domain name you’re adding to Google Apps. Scroll down to the Google Apps section, and paste your code from Google Apps into the verification code field.  Click Generate DNS records when you’re done. This will add the needed DNS settings to your records in the box above the Google Apps section.  Click Save DNS records. Now, go back to the Google Apps signup page, and click I’ve completed the steps above. Authenticate Google Apps on Your Own Server If your website is hosted on your own server or hosting account, you’ll need to take a few more steps to add Google Apps to your domain.  You can add a CNAME record to your domain host using the same information that you would use with a WordPress account, or you can upload an HTML file to your site’s main directory.  In this test we’re going to upload an HTML file to our site for verification. Copy the code under #1, which should be something like googleabcdefg123456.  Do not click the button at the bottom; wait until we’ve completed the next step first. Create a new HTML file and paste the code in it.  You can do this easily in Notepad: create a new document, paste the code, and then save as googlehostedservice.html.  Make sure to select the type as All Files or otherwise the file will have a .txt extension. Upload this file to your web server via FTP or a web dashboard for your site.  Make sure it is in the top level of your site’s directory structure, and try visiting it at yoursite.com/googlehostedservice.html. Now, go back to the Google Apps signup page, and click I’ve completed the steps above. Setup Your Email on Google Apps When this is done, your Google Apps account should be activated and ready to finish setting up.  Google Apps will offer to launch a guide to step you through the rest of the process; you can click Launch guide if you want, or click Skip this guide to continue on your own and go directly to the Apps dashboard.   If you choose to open the guide, you’ll be able to easily learn the ropes of Google Apps administration.  Once you’ve completed the tutorial, you’ll be taken to the Google Apps dashboard. Most of the Google Apps will be available for immediate use, but Email may take a bit more setup.  Click Activate email to get your Gmail-powered email running on your domain.    Add Google MX Records to Your Server You will need to add Google MX records to your domain registrar in order to have your mail routed to Google.  If your domain is hosted on WordPress.com, you’ve already made these changes so simply click I have completed these steps.  Otherwise, you’ll need to manually add these records before clicking that button.   Adding MX Entries is fairly easy, but the steps may depend on your hosting company or registrar.  With some hosts, you may have to contact support to have them add the MX records for you.  Our site’s host uses the popular cPanel for website administration, so here’s how we added the MX Entries through cPanel. Add MX Entries through cPanel Login to your site’s cPanel, and click the MX Entry link under Mail. Delete any existing MX Records for your domain or subdomain first to avoid any complications or interactions with Google Apps.  If you think you may want to revert to your old email service in the future, save a copy of the records so you can switch back if you need. Now, enter the MX Records that Google listed.  Here’s our account after we added all of the entries to our account. Finally, return to your Google Apps Dashboard and click the I have completed these steps button at the bottom of the page. Activating Service You’re now officially finished activating and setting up your Google Apps account.  Google will first have to check the MX records for your domain; this only took around an hour in our test, but Google warns it can take up to 48 hours in some cases. You may then see that Google is updating its servers with your account information.  Once again, this took much less time than Google’s estimate. When everything’s finished, you can click the link to access the inbox of your new Administrator email account in Google Apps. Welcome to Gmail … at your own domain!  All of the Google Apps work just the same in this version as they do in the public @gmail.com version, so you should feel right at home. You can return to the Google Apps dashboard from the Administrative email account by clicking the Manage this domain at the top right. In the Dashboard, you can easily add new users and email accounts, as well as change settings in your Google Apps account and add your site’s branding to your Apps. Your Google Apps will work just like their standard @gmail.com counterparts.  Here’s an example of an inbox customized with the techinch logo and a Gmail theme. Links to Remember Here are the common links to your Google Apps online.  Substitute your domain or subdomain for yourdomain.com. Dashboard https://www.google.com/a/cpanel/yourdomain.com Email https://mail.google.com/a/yourdomain.com Calendar https://www.google.com/calendar/hosted/yourdomain.com Docs https://docs.google.com/a/yourdomain.com Sites https://sites.google.com/a/yourdomain.com Conclusion Google Apps offers you great webapps and webmail for your domain, and let’s you take advantage of Google’s services while still maintaining the professional look of your own domain.  Setting up your account can be slightly complicated, but once it’s finished, it will run seamlessly and you’ll never have to worry about email or collaboration with your team again. Signup for the free Google Apps Standard Similar Articles Productive Geek Tips Mysticgeek Blog: Create Your Own Simple iGoogle GadgetAccess Your Favorite Google Services in Chrome the Easy WayRevo Uninstaller Pro [REVIEW]Mysticgeek Blog: A Look at Internet Explorer 8 Beta 1 on Windows XPFind Similar Websites in Google Chrome TouchFreeze Alternative in AutoHotkey The Icy Undertow Desktop Windows Home Server – Backup to LAN The Clear & Clean Desktop Use This Bookmarklet to Easily Get Albums Use AutoHotkey to Assign a Hotkey to a Specific Window Latest Software Reviews Tinyhacker Random Tips Xobni Plus for Outlook All My Movies 5.9 CloudBerry Online Backup 1.5 for Windows Home Server Snagit 10 Video preview of new Windows Live Essentials 21 Cursor Packs for XP, Vista & 7 Map the Stars with Stellarium Use ILovePDF To Split and Merge PDF Files TimeToMeet is a Simple Online Meeting Planning Tool Easily Create More Bookmark Toolbars in Firefox

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  • Implementing an automatic navigation mesh generation for 2d top down map?

    - by J2V
    I am currently in the middle of implementing an A* pathfinding for enemies. In order to implement the actual A* logic, I need a navigation mesh for my map. I am working on a 2D top down rpg map. The world is static, meaning there is no requirement for dynamic runtime mesh generation. My world objects are pixel based, not tile based and have associated data with them such as scale, rotation, origin etc. I will obviously need some vertex data being generated from my world objects, maybe create a polygon generation from color data? I could create a colormap with objects for my whole map, but I have no idea how to begin creating nav mesh polygons. How would an actual navigation mesh generation look like with this kind of available information? Can anyone maybe point to some great resources? I have looked into some 3D nav mesh tools, but they seem kind of overly complex for my situation and also have a lot of their req data available from models. Thanks a lot in advance! I have been trying to get my head around it for some time now.

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  • Silverlight ProgressBar issues with Binding

    - by Chris Skardon
    The ProgressBar pretty much does what it says on the tin, displays progress, in a bar form (well, by default anyhow). It’s pretty simple to use: <ProgressBar Minimum="0" Maximum="100" Value="50"/> Gives you a progress bar with 50% of it filled: Easy! But of course, we’re wanting to use binding to change the value, again, pretty easy, have a ViewModel with a ‘Value’ in it, and bind: <ProgressBar Minimum="0" Maximum="100" Value="{Binding Value}"/> Spiffy, and whilst we’re at it, why not bind the Maximum value as well – after all, we can’t be sure of the size of the progress, and it’s a pain to have to work out the percentage (when the progress bar can do it for us): <ProgressBar Minimum="0" Maximum="MaximumValue" Value="{Binding Value}"/> Right, this will work absolutely fine. Or will it??? On the face of it, it looks good, and testing it shows no issues, until at one point we go from: Maximum = 100; Value = 90; to Maximum=60; Value=50; On the face of it not unreasonable. The problem is more obvious if we look at the states of the properties after each set (initially Maximum is set at 1, Value = 0): Code Maximum Value Value < Maximum Maximum = 100; 100 0 True Value = 90; 100 90 True Maximum = 60; 60 90 False Value = 50; 60 50 True Everything is good until the Value is less than the Maximum, at this point the Progress Bar breaks. That’s right, it no longer updates itself, it will always look 100% full. The simple solution – always ensuring you set Value before Maximum is fine unless you’re using a ProgressBar in a less controlled environment – where for example you’re setting a ‘container’ with both values at the same time. The example I have is in a DataTemplate, I have a DataTemplate for a BusyIndicator, (specifically the BusyContentTemplate). The binding works this way: <BusyIndicator BusyContent="{Binding BusyContent}" BusyContentTemplate="{Binding ProgressTemplate}"/> With the template as the ProgressBar defined above… I was setting my BusyContent like this: BusyContent = content; aaaaaand finally, ‘content’ is a class: public class ContentClass : INotifyPropertyChanged { //Obviously this is properly implemented… public double Maximum { get;set;} public double Value { get;set;} } Soooo… As I was replacing the BusyContent wholesale, the order of the binding being set was outside of my control, so – how to go about it? Basically? Fudge it. Modify the ContentClass to include a method: public void Update(double value, double max) { Value = value; Maximum = max; } and change where the setting is to be: BusyContent.Update(content.Value, content.Maximum); Thereby getting the order correct.. Obvious really. Meh :|

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  • What is the best way to render a 2d game map?

    - by Deukalion
    I know efficiency is key in game programming and I've had some experiences with rendering a "map" earlier but probably not in the best of ways. For a 2D TopDown game: (simply render the textures/tiles of the world, nothing else) Say, you have a map of 1000x1000 (tiles or whatever). If the tile isn't in the view of the camera, it shouldn't be rendered - it's that simple. No need to render a tile that won't be seen. But since you have 1000x1000 objects in your map, or perhaps less you probably don't want to loop through all 1000*1000 tiles just to see if they're suppose to be rendered or not. Question: What is the best way to implement this efficiency? So that it "quickly/quicker" can determine what tiles are suppose to be rendered? Also, I'm not building my game around tiles rendered with a SpriteBatch so there's no rectangles, the shapes can be different sizes and have multiple points, say a curved object of 10 points and a texture inside that shape; Question: How do you determine if this kind of objects is "inside" the View of the camera? It's easy with a 48x48 rectangle, just see if it X+Width or Y+Height is in the view of the camera. Different with multiple points. Simply put, how to manage the code and the data efficiently to not having to run through/loop through a million of objects at the same time.

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  • How to read default key value with dconf or gsettings?

    - by Zta
    I would like to know the default value of a dconf/gsettings key. My question is a followup of the question below: Where can I get a list of SCHEMA / PATH / KEY to use with gsettings? What I'm trying to do, so create a script that reads all my personal preferences so I can back them up and restore them. I plan to iterate though all keys, like the script above, see what keys have been changed from their default value, and make a note of these, that can be restored later. I see that the dconf-editor display the keys' default value, but I'd very much like to script this. Also, I don't see how parsing the schemas /usr/share/glib-2.0/schemas/ can be automated. Maybe someone can help? gsettings get-default|list-defaults would be nice =) (Geesh, it was much easier in the old days where you just kept your ~/.somethingrc in subversion ... =\ Based on the answer given below, I've updated the script to print schema, key, key's data type, default value, and actual value: #!/bin/bash for schema in $(gsettings list-schemas | sort); do for key in $(gsettings list-keys $schema | sort); do type="$(gsettings range $schema $key | tr "\n" " ")" default="$(XDG_CONFIG_HOME=/tmp/ gsettings get $schema $key | tr "\n" " ")" value="$(gsettings get $schema $key | tr "\n" " ")" echo "$schema :: $key :: $type :: $default :: $value" done done This workaround basically covers what I need. I'll continue working on the backup scrip from here.

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