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  • About the forward and backward a word behaviour in Emacs

    - by janoChen
    I don't know if there's something wrong with my settings but when I press M-f (forward a word) it doesn't matter where I am, it never place the cursor in the next word (just between words). This doesn't happen with M-b which place my cursor in the beginning of the previous word. Is this a normal behavior? How do I place my cursor at the beginning of the following word?

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  • WPF: Copy Property to Clipboard

    - by Phil Sandler
    I have a string property in my ViewModel/Datacontext and want a simple button that copies its contents to the clipboard. Is this possible to do from XAML, or I do I need to handle the button click event (or use an ICommand) to accomplish this? I thought the following would work, but my button is always greyed out: <Button Width="100" Content="Copy" Command="ApplicationCommands.Copy" CommandTarget="{Binding MyStringProperty}"/>

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  • Using Javascript in Adobe Reader

    - by godleuf
    Hi, I am currently using the following script for a few documents: var pp = this.getPrintParams(); pp.interactive = pp.constants.interactionLevel.automatic; this.print(pp); How do I add another command, say document.close() so that it reads the print function and then follows the close document last? Do I simply add the close command right after the print command so it would read var pp = this.getPrintParams(); pp.interactive = pp.constants.interactionLevel.automatic; this.print(pp); document.close(); Thanks.

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  • Disable comments in stdout (DOS)

    - by Shadi
    If I use Dos command "copy" to concatenate two files: copy a1.txt + a2.txt a.txt I will have something like the following in stdout: C:\a1.txt C:\a2.txt 1 file(s) copied. I do not want to have anything written in stdout, I mean, I just want to have 'a.txt' without those 3 lines written in stdout. Is there any way to do so? the reason is, I need speed and I know that any IO takes time. Thanks, Shadi.

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  • MySQL select two tables at the same time...

    - by Jerry
    Hi all I have two tables and want to make a query. I tried to get team AA and team BB's image base on table A. I used: SELECT tableA.team1, tableA.team2, tableB.team, tableB.image, FROM tableA LEFT JOIN tableB ON tableA.team1=tableB.team The result only display imageA on the column. Are there any ways to select imageA and image B without using the second query? I appreciate any helps! Thanks a lot! My table structure are: table A team1 team2 ------------ AA BB table B team image ------------- AA imagaA BB imageB

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  • Asp.Net - Can a LinkButton.CommandArgument be typed?

    - by Stimul8d
    Okay so given a LinkButton inside a the ItemTemplate of a Repeater declared like this - <asp:LinkButton ID="restrictionDelete" runat="server" CssClass="restrictionDelete" Text="Delete..." OnCommand="lnkDeleteRestriction_Command" CommandName="Delete" CommandArgument="<%# Container.DataItem %>"></asp:LinkButton> Now,..the repeater is being bound to a list of Restriction objects so when the lnkDeleteRestriction_Command is fired I'm expecting that I can cast the CommandEventArgs.CommandArgument which is an object to my Restriction type. This doesn't seem to be so,..I just get the fully qualified type name as a string. Can I receive a typed command argument at all and if not, why is it an object? Thanks in advance,

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  • Why does starting a process in the background prevent me from recalling previous commands in the command prompt?

    - by leeand00
    I'm running asynchronous command prompt commands in cmd on Windows 7 64-bit and for some reason it effects my ability to recall previous commands just after I run them; for example: I might run something like: start /B rmdir /Q /S .\some_massive_directory And next I try to press the up arrow to recall the text of the previous command..but nothing happens...is this because whatever data structure is holding my commands is locked by the process I sent to the background, or is it because I am using a network mapped drive to run my command on?

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  • Bash completion doesn't work, or is ignoring what I've typed; but works for commands

    - by Neil Traft
    Bash completion seems to be ignoring what I've typed (it tries to complete, but acts as if there's nothing under the cursor). I know I saw it work on this machine earlier today, but I'm not sure what has changed. Some examples: cd shows all directories under my current folder: $ cd co<tab><tab> cmake/ config/ doc/ examples/ include/ programs/ sandbox/ src/ .svn/ tests/ Commands like ls and less show all files and directories under my current folder: $ ls co<tab><tab> cmake/ config/ .cproject Doxyfile.in include/ programs/ README.txt src/ tests/ CMakeLists.txt COPYING.txt doc/ examples/ mainpage.dox .project sandbox/ .svn/ Even when I try to complete things from a different folder, it gives me only the results for my current folder (telling me that it is completely ignoring what I've typed): $ cd ~/D<tab><tab> cmake/ config/ doc/ examples/ include/ programs/ sandbox/ src/ .svn/ tests/ But it seems to be working fine for commands and variables: $ if<tab><tab> if ifconfig ifdown ifnames ifquery ifup $ echo $P<tab><tab> $PATH $PIPESTATUS $PPID $PS1 $PS2 $PS4 $PWD $PYTHONPATH I do have this bit in my .bashrc, and I have confirmed that my .bashrc is indeed getting sourced: if [ -f /etc/bash_completion ] && ! shopt -oq posix; then . /etc/bash_completion fi I've even tried manually executing that file, but it doesn't fix the problem: $ . /etc/bash_completion There was even one point in time where it was working for ls, but was not working for cd ... but I can't replicate that result now. Update: I also just discovered that I have terminals open from earlier that still work. I ran source .bashrc in one of them and afterwards completion was broken. Here is my .bashrc: # ~/.bashrc: executed by bash(1) for non-login shells. # see /usr/share/doc/bash/examples/startup-files (in the package bash-doc) # for examples # # Modified by Neil Traft #source ~/.profile # Allow globs to expand hidden files shopt -s dotglob nullglob # If not running interactively, don't do anything [ -z "$PS1" ] && return # don't put duplicate lines or lines starting with space in the history. # See bash(1) for more options HISTCONTROL=ignoreboth # append to the history file, don't overwrite it shopt -s histappend # for setting history length see HISTSIZE and HISTFILESIZE in bash(1) HISTSIZE=1000 HISTFILESIZE=2000 # check the window size after each command and, if necessary, # update the values of LINES and COLUMNS. shopt -s checkwinsize # If set, the pattern "**" used in a pathname expansion context will # match all files and zero or more directories and subdirectories. #shopt -s globstar # make less more friendly for non-text input files, see lesspipe(1) [ -x /usr/bin/lesspipe ] && eval "$(SHELL=/bin/sh lesspipe)" # set variable identifying the chroot you work in (used in the prompt below) if [ -z "$debian_chroot" ] && [ -r /etc/debian_chroot ]; then debian_chroot=$(cat /etc/debian_chroot) fi # Color the prompt export PS1="\[$(tput setaf 2)\]\u@\h:\[$(tput setaf 5)\]\W\[$(tput setaf 2)\] $\[$(tput sgr0)\] " # enable color support of ls and also add handy aliases if [ -x /usr/bin/dircolors ]; then test -r ~/.dircolors && eval "$(dircolors -b ~/.dircolors)" || eval "$(dircolors -b)" alias ls='ls --color=auto' #alias dir='dir --color=auto' #alias vdir='vdir --color=auto' alias grep='grep --color=auto' alias fgrep='fgrep --color=auto' alias egrep='egrep --color=auto' fi # Add an "alert" alias for long running commands. Use like so: # sleep 10; alert alias alert='notify-send --urgency=low -i "$([ $? = 0 ] && echo terminal || echo error)" "$(history|tail -n1|sed -e '\''s/^\s*[0-9]\+\s*//;s/[;&|]\s*alert$//'\'')"' # Alias definitions. # You may want to put all your additions into a separate file like # ~/.bash_aliases, instead of adding them here directly. # See /usr/share/doc/bash-doc/examples in the bash-doc package. if [ -f ~/.bash_aliases ]; then . ~/.bash_aliases fi # enable programmable completion features (you don't need to enable # this, if it's already enabled in /etc/bash.bashrc and /etc/profile # sources /etc/bash.bashrc). if [ -f /etc/bash_completion ] && ! shopt -oq posix; then . /etc/bash_completion fi

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  • Installing paperclip plugin

    - by mnml
    I'm trying to install the paperclip plugin with the following command: ruby script/plugin install git://github.com/thoughtbot/paperclip.git But I'm getting some errors: ruby script/plugin install git://github.com/thoughtbot/paperclip.git --force svn: '/home/app/vendor/plugins' is not a working copy /usr/lib/ruby/1.8/open-uri.rb:32:in `initialize': No such file or directory - git://github.com/thoughtbot/paperclip.git (Errno::ENOENT) from /usr/lib/ruby/1.8/open-uri.rb:32:in `open_uri_original_open' from /usr/lib/ruby/1.8/open-uri.rb:32:in `open' from ./script/../config/../vendor/rails/railties/lib/commands/plugin.rb:863:in `fetch_dir' from ./script/../config/../vendor/rails/railties/lib/commands/plugin.rb:857:in `fetch' from ./script/../config/../vendor/rails/railties/lib/commands/plugin.rb:856:in `each' from ./script/../config/../vendor/rails/railties/lib/commands/plugin.rb:856:in `fetch' from ./script/../config/../vendor/rails/railties/lib/commands/plugin.rb:219:in `install_using_http' from ./script/../config/../vendor/rails/railties/lib/commands/plugin.rb:169:in `send' from ./script/../config/../vendor/rails/railties/lib/commands/plugin.rb:169:in `install' from ./script/../config/../vendor/rails/railties/lib/commands/plugin.rb:734:in `parse!' from ./script/../config/../vendor/rails/railties/lib/commands/plugin.rb:732:in `each' from ./script/../config/../vendor/rails/railties/lib/commands/plugin.rb:732:in `parse!' from ./script/../config/../vendor/rails/railties/lib/commands/plugin.rb:447:in `parse!' from ./script/../config/../vendor/rails/railties/lib/commands/plugin.rb:463:in `parse!' from ./script/../config/../vendor/rails/railties/lib/commands/plugin.rb:871 from script/plugin:3:in `require' from script/plugin:3 Is it because I'm using a old rails version?

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  • Open source app to manage and run commands on cloud servers? [closed]

    - by Mark Theunissen
    I'm creating a SaaS platform, and I need a component / library that can create, delete and store the connection details for cloud servers. It also needs to support executing shell commands on these servers and returning the response to the caller. I want a central database of servers and their configuration, plus the ability to reach out and manage the servers via SSH execution of bash scripts. I don't want something that needs agents on every server like Chef. For example, this command is received by the hypothetical application: CREATE USER server = server12345 name = myuser It's translated into the following set of actions and executed by the app, which knows how to connect to server12345, and how to create a user on that server: $ ssh root@server12345 $ adduser myuser And returns the output from the shell: Added user myuser. I've done research on Google and can't quite quite find something that does this already. I've found: fabric This part handles the executing of the shell commands very elegantly, and can take multiple server definitions, but it's supposed to be a deployment tool so doesn't do everything that would be required above - for example, it doesn't have a daemon mode where it listens for commands - it expects to be executed on the shell. It also can't provide the central database functionality. libcloud This library can handle the server admin (CRUD) part, but doesn't have a command interface daemon either, and doesn't let you execute commands on the servers. I guess I need something that is a combination of libcloud, fabric and django for an API. Or something else that does that same thing regardless of language. Overmind Overmind is a GUI and wrapper around libcloud, but doesn't support the command execution part. What am I missing here?

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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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  • Html5: How to handle RGB pixel with commands from prompt ? (just a browser)

    - by Rocket Surgeon
    In the browser tools, say in debugging (any browser will do, but IE9 preferred) how can I access things like html5 canvas and modify individual pixels by typing commands from prompt ? I know, it is possible to accomplish in miriad normal ways with preparing the markup and loading the page, but what is the shortest path ? The browser is running with some content, then I hit F12-Console- what exactly should I type to cause a canvas to change ? Thank you

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  • Why are the man pages for gvfs-commands not in Ubuntu?

    - by Pili Garcia
    These are the man pages for gvfs-cat gvfs-less gvfs-monitor-dir gvfs-move gvfs-rm gvfs-trash gvfs-copy gvfs-ls gvfs-monitor-file gvfs-open gvfs-save gvfs-tree gvfs-info gvfs-mkdir gvfs-mount gvfs-rename gvfs-set-attribute http://www.unix.com/man-pages.php?query=gvfs-info&apropos=0&section=1&os=opensolaris Every year I see that there are more commands without manpage nor apropose description, nothing! Is that the path?

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  • Is there a way to submit a batch of commands to a Cisco router and have them execute from the router?

    - by atroon
    I need to change the configuration of a remote (6 hours' drive) client's Cisco 871 (IOS 12.4.15T) from my location because of some new internet service at his location. To be more precise, I need to change the default route, ip address of the outside interface (Fa4) and disable the PPPoE setup there. Unfortunately, doing any of this will (obviously) break the connection to the router. I do not have an out-of-band management modem set up (I know, I know). Is there any way to enter the commands I need to have run and have them execute one after the other, from a file on flash:? I have never tried anything like that before. Essentially a DOS-style batch file is exactly what I need. Nothing like it seems to be out there except using kron to execute CLI commands, but that is specified here as only taking EXEC commands, not configuration ones. Is there hope, or do I travel?

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  • How to create an MSI package that installs no files and only executes some commands using Wix

    - by Sevas
    I am trying to create an MSI package that uses the AppCmd application to configure IIS7. It only has to execute some commands that call AppCmd. Some commands need to be called when installing, other commands need to be called when uninstalling. Here is what I have now: I have a property that points to AppCmd: <Property Id="APPCMD" Value="C:\Windows\system32\inetsrv\appcmd.exe" /> I have my custom actions: <CustomAction Id="UnlockHandlerSection" Return="check" Property="APPCMD" ExeCommand="unlock config /section:system.webServer/handlers" /> I have Custom elements that call the actions: <InstallExecuteSequence> <Custom Action="UnlockHandlerSection" After="InstallFiles">NOT Installed AND NOT PATCH</Custom> <InstallExecuteSequence> The problem with this is is that the commands are not called when I try to install the resulting MSI package. Could anyone please advise me on what I am doing wrong? Thank you!

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  • How do you assign commands to keys in Terminal?

    - by NES
    Is there a solution to assign special key combinations to words in terminal use. For example the less command is very usefull and i use i a lot to pipe the output of another process through it. The idea would be to set up special key combinations that are only active in terminal use assigned to write different commands? So pressing CTRL + l in terminal window could write | less or CTRL + G could stand for | grep Note: i just mean adding the letters to commandline not execute the finally. A similar way what's tabcompletion but more specific.

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  • how to find 3g modem signal strength with out AT commands?

    - by neckTwi
    when i try to find signal strength of my modem using AT+CSQ, the usb device is locked by the network manager. To find the signal strength with AT+CSQ i have to first disable network connection using #nmcli nm wwan off to unlock the device inode /dev/ttyUSBX. Is there any nmcli option to get signal strength or any other option? EDIT The gdbus object for NetworkManager don't have any method like getSignalStrength. Network manager is locking device file preventing to use AT commands. nm-applet was able to display signal strength in system tray. so there should be a way to get signal strength form network manager! nmcli is command line counter part of nm-applet. Can i get signal strength using nmcli? nothing about signal strength is mentioned in its man pages.

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  • How do global cancel/exit commands work in bash?

    - by SecurityGate
    As I have done multiple times before, I've written bash scripts, and just general commands that go nowhere. They just blink the little command line cursor at me for infinity until I control+C the command. When I do cancel the command, what exactly is going on when I do this? Am I somehow stopping and killing the current PID I'm working on? Does it jump to a different run-level and execute something to terminate the command? On a slightly different note, I've never been able to figure out how to set up something like this in a script or program I've worked on. Since I mostly program in Ruby, can I setup something like a certain key press stops the program? Every time I've looked into doing something similar, I always end up getting hung up when it comes to user input, whether that is a loop waiting for a condition, or something like this: def Break() user_break = gets.strip end def Main() Function1() Break() Function2() Break() [...] end It seems and is incredibly bulky, and definitely isn't easily scaled up or down.

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  • possible to use an IP derived from Dynamic DNS in htaccess IP allow/deny commands?

    - by user115745
    On a website I manage, I want to use an .htaccess file to allow access to a certain administrative directory only from my home IP address, which is dynamically assigned by my ISP and therefore changes -- not regularly, but it does happen. I also have an account from DynDNS and have one of the auto-update clients making sure it always points to my actual home IP address. I don't actually host anything at home; I just have set up the Dynamic DNS account. Is there any way to combine these features: that is, is it possible write the .htaccess allow/deny commands at my outside webhost in a way that my home IP address is not hard coded into the command, but instead is somehow derived from the Domain Name that the DynDNS has assigned me, by doing a real-time lookup every time the directory's .htaccess file is hit? Thank you.

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  • How do you assign commands to keys to in Terminal?

    - by NES
    Is there a solution to assign special key combinations to words in terminal use. For example the less command is very usefull and i use i a lot to pipe the output of another process through it. The idea would be to set up special key combinations that are only active in terminal use assigned to write different commands? So pressing CTRL + l in terminal window could write | less or CTRL + G could stand for | grep Note: i just mean adding the letters to commandline not execute the finally. A similar way what's tabcompletion but more specific.

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  • How do I limit the users a specific user can run commands in linux?

    - by user8571
    I have 2 user accounts, foo and bar I want to allow user foo to execute commands as root and any other user ie: sudo su root -c'./run-my-script' sudo su bar -c'./another-script' sudo su another -c'./yet-another-script I also want to allow user bar to execute commands as other user but only a subset and not root ie: sudo su bar -c'./run-my-script' but not sudo su root -c'./run-my-script' Is this possible ?

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  • Is it possible to control the whole Gnome desktop with vi-like commands?

    - by roy
    I know with readline you can use emacs or vi commands to edit the input of several interactive text programs. I wonder if there exists such a similar facility to control the whole desktop in Gnome or in any other desktop environment. Maybe it could be a program that intercepts keystrokes and process them in the way vi does, translating sequences of characters to desktop commands and delivering to the active window only the text that is writen in insert mode. Do you know some tool like that?

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  • How copy with shell commands(Linux) from 1 computer have (permanent url + open port) to 2 computer (secure way)?

    - by BenBen
    How copy with shell commands(Linux) from remote(my office computer) computer (permanent url + open port) to my (home) computer home/remote_computer_user/Desktop/test1.txt to my home computer home/home_computer_user/Downloads/ ? What I am doing: 1. ssh <user>@<computer1address> -p <port> :: success to get remote computer shell () 2. (I think I should use scp , but I dont how exactly in my case) Please if you can, write the exact commands that i should to from the shell Thanks in advance

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