    irb(main):001:0&gt; a = [1, 2, 3, 4, 5]
    =&gt; [1, 2, 3, 4, 5]
    irb(main):002:0&gt; b = [1, 2, 4, 6]
    =&gt; [1, 2, 4, 6]
    irb(main):003:0&gt; a - b
    =&gt; [3, 5]
    irb(main):005:0&gt; b - a
    =&gt; [6]
    irb(main):006:0&gt;

I have a web application that relies on some resources and parameters to be configured after it is installed, like a JDBC connection.

What I have come up with is providing a `META-INF/context.xml` which is copied into `[engine-name]/[server-name]/[app-name].xml` by Tomcat when I deploy the application. This way all I am providing is a war file that can be copied into the appBase folder (webapps).
Tomcat&#39;s documentation [says][1] if there is such a file it won&#39;t be overwritten which is really great, since the changes made after deployment won&#39;t be lost.

But there is a subtle issue here:
Since we deploy the application by copying into webapps directory, Tomcat will first uninstall the existing application as well as the configuration file. This way the configuration file will be lost / overwritten which is not desirable.
Tomcat [won&#39;t][2] modify this behaviour as far as I know.

The question is:
Is there a way to work around this issue by installing the application in a way that Tomcat won&#39;t remove the existing configuration file.
Or, is there a better way of packaging the application?

Please note that we don&#39;t want to set autoDeploy to false and we cannot use human intervention for the installation (which rules out using Tomcat Manager web application).

If I get the configuration file out of .war file and copy it separately as `[engine-name]/[server-name]/[app-name].xml`, Tomcat will still associate it with my application and remove it once I copy a new .war file.

Another assumption is: We don&#39;t know in advance the values to the configuration. We will only provide a sample configuration (a placeholder, if you wish) while actual configuration will be performed at some time later (not necessarily in the installation time). 

Thanks

  [1]: http://tomcat.apache.org/tomcat-5.5-doc/config/context.html
  [2]: https://issues.apache.org/bugzilla/show_bug.cgi?id=44879

How to provide a context configuration for a web application in Tomcat?

I&#39;m trying to write an array (list?) to a text file using Python 3. Currently I have:

    def save_to_file(*text):

        with open(&#39;/path/to/filename.txt&#39;, mode=&#39;wt&#39;, encoding=&#39;utf-8&#39;) as myfile:
            for lines in text:
                print(lines, file = myfile)
        myfile.close

This writes what looks like the array straight to the text file, i.e.,

    [&#39;element1&#39;, &#39;element2&#39;, &#39;element3&#39;]
    username@machine:/path$

What I&#39;m looking to do is create the file with

    element1
    element2
    element3
    username@machine:/path$

I&#39;ve tried different ways to loop through and append a &quot;\n&quot; but it seems that the write is dumping the array in one operation. The question is similar to https://stackoverflow.com/questions/5429064/how-to-write-list-of-strings-to-file-adding-newlines but the syntax looked like it was for Python 2? When I tried a modified version of it:

    def save_to_file(*text):

        myfile = open(&#39;/path/to/filename.txt&#39;, mode=&#39;wt&#39;, encoding=&#39;utf-8&#39;)
        for lines in text:
            myfile.write(lines)
        myfile.close

...the Python shell gives &quot;TypeError: must be str, not list&quot; which I think is because of changes between Python2 and Python 3. What am I missing to get each element on a newline?

EDIT: Thank you to @agf and @arafangion; combining what both of you wrote, I came up with:

    def save_to_file(text):

        with open(&#39;/path/to/filename.txt&#39;, mode=&#39;wt&#39;, encoding=&#39;utf-8&#39;) as myfile:
            myfile.write(&#39;\n&#39;.join(text))
            myfile.write(&#39;\n&#39;)

It looks like I had part of the issue with &quot;*text&quot; (I had read that expands arguments but it didn&#39;t click until you wrote that [element] was becoming [[element]] that I was getting a str-not-list type error; I kept thinking I needed to tell the definition that it was getting a list/array passed to it and that just stating &quot;test&quot; would be a string.) It worked once I changed it to just text and used myfile.write with join, and the additional \n puts in the final newline at the end of the file.

How to write a list to a file with newlines in Python3

&gt; **Possible Duplicate:**  
&gt; [diff a ruby string or array](https://stackoverflow.com/questions/80091/diff-a-ruby-string-or-array)  

&lt;!-- End of automatically inserted text --&gt;

I have an old array: `[1, 2, 3, 4, 5]`, and new: `[1, 2, 4, 6]`

How to get difference with Ruby: that `5, 3` was removed and `6` was added?

Get difference of arrays in Ruby

> Possible Duplicate: 
> <a href="https://stackoverflow.com/questions/80091/diff-a-ruby-string-or-array" target="_blank" rel="noopener noreferrer">diff a ruby string or array</a>

I have an old array: <code>[1, 2, 3, 4, 5]</code>, and new: <code>[1, 2, 4, 6]</code>
How to get difference with Ruby: that <code>5, 3</code> was removed and <code>6</code> was added?

My situation:

    var id_tag = [1,2,3,78,5,6,7,8,47,34,90];

I would like to *`delete where id_tag = 90`* and to return:

    var id_tag = [1,2,3,78,5,6,7,8,47,34];

How can I do that?

Javascript - remove an array item by value

Lets have a look at an example.

    var arr1 = new Array({name: &quot;lang&quot;, value: &quot;English&quot;},
                         {name: &quot;age&quot;, value: &quot;18&quot;});

    var arr2 = new Array({name : &quot;childs&quot;, value: &#39;5&#39;},
                         {name: &quot;lang&quot;, value: &quot;German&quot;});

I need to merge those 2 arrays of objects and create the following array:

    var arr3 = new Array({name: &quot;lang&quot;, value: &quot;German&quot;},
                         {name: &quot;age&quot;, value: &quot;18&quot;},
                         {name : &quot;childs&quot;, value: &#39;5&#39;});

Is there any JavaScript or jQuery function to do this?

`$.extend` doesn&#39;t suit me. It returns

    var arr4 = new Array({name : &quot;childs&quot;, value: &#39;5&#39;},
                         {name: &quot;lang&quot;, value: &quot;German&quot;});

Merge 2 arrays of objects

Is there a more correct way to output the contents of an array as a comma delimited string

    @emails = [&quot;joe@example.com&quot;, &quot;Peter@example.com&quot;, &quot;alice@example.com&quot;]
    
    @emails * &quot;,&quot;
    
    =&gt; &quot;joe@example.com&quot;, &quot;Peter@example.com&quot;, &quot;alice@example.com&quot;

This works but I am sure there must be a more elegant solution.

Ruby output contents of an array as a comma separated string Ruby

For some reason, it looks like I cannot pass array of strings as parameter to scriptblock. What am I doing here wrong?

My script which is called from another script:

    param(
        [parameter(Mandatory=$true)]
        [string[]]$myarr
    )

    foreach ($elem in $myarr){
        $elem
    }

I call it from another script as

     $myarr = @(&quot;111&quot;, &quot;222&quot;)
     start-job -filepath myscript.ps1 -arg $myarr

I got only the first item in the array - &quot;111&quot;.


How do I pass an array as a parameter to another script?

Assume you have a basic `Employee` class as such:
    
    class Employee
    {
       public string Name;
       public int Years;
       public string Department;
    }


Then (in a seperate class) I have the following code fragments (I think i understand all but the last):


I believe that the following code fragment works because the array initiliser creates an array of Employee objects which are the same type as the workforce variable being assigned to.

    Employee[] workforceOne = new Employee[] {
       new Employee() { Name = &quot;David&quot;, Years = 0, Department = &quot;software&quot; },
       new Employee() { Name = &quot;Dexter&quot;, Years = 3, Department = &quot;software&quot; },
       new Employee() { Name = &quot;Paul&quot;, Years = 4, Department = &quot;software&quot; } };


I then have the following code fragment.  I believe this works because the array of `Employee` objects implicity is an implementation of the Array() class which implements `IEnumerable`.  Therefore, I believe this is why the array can be assigned to IEnumerable?

    IEnumerable workforceTwo = new Employee[] {
       new Employee() { Name = &quot;David&quot;, Years = 0, Department = &quot;software&quot; },
       new Employee() { Name = &quot;Dexter&quot;, Years = 3, Department = &quot;software&quot; },
       new Employee() { Name = &quot;Paul&quot;, Years = 4, Department = &quot;software&quot; } };


Then I have this code fragment:

    IEnumerable&lt;Employee&gt; workforceThree = new Employee[] {
       new Employee() { Name = &quot;David&quot;, Years = 0, Department = &quot;software&quot; },
       new Employee() { Name = &quot;Dexter&quot;, Years = 3, Department = &quot;software&quot; },
       new Employee() { Name = &quot;Paul&quot;, Years = 4, Department = &quot;software&quot; } };

**I am not sure why this code fragment works?**  `IEnumerable&lt;Employee&gt;` inherits from `IEnumerable` (and overrides (or overloads?) the `GetEnumerator()` method) but shouldn&#39;t i therefore need a cast for the above to work as such:

    //The cast does work but is not required
    IEnumerable&lt;Employee&gt; workforceFour = (IEnumerable&lt;Employee&gt;)new Employee[] {
       new Employee() { Name = &quot;David&quot;, Years = 0, Department = &quot;software&quot; },
       new Employee() { Name = &quot;Dexter&quot;, Years = 3, Department = &quot;software&quot; },
       new Employee() { Name = &quot;Paul&quot;, Years = 4, Department = &quot;software&quot; } };

It seems that the array is being implicitly down cast from a type of `IEnumerable` to `IEnumerable&lt;Employee&gt;` but I always thought when you needed to convert a type to something more specific you needed an explicit cast.


Maybe i&#39;m missing something simple in my understanding here but can someone please help me with my understanding around this.

Thank you.

Casting array to IEnumerable&lt;T&gt;

I have a User model that belongs to a Group. Group must have unique name attribute. User factory and group factory are defined as:

    Factory.define :user do |f|
      f.association :group, :factory =&gt; :group
      # ...
    end

    Factory.define :group do |f|
      f.name &quot;default&quot;
    end

When the first user is created a new group is created too. When I try to create a second user it fails because it wants to create same group again.

Is there a way to tell factory_girl association method to look first for an existing record?

Note: I did try to define a method to handle this, but then I cannot use f.association. I would like to be able to use it in Cucumber scenarios like this:

    Given the following user exists:
      | Email          | Group         |
      | test@email.com | Name: mygroup |

and this can only work if association is used in Factory definition.

Find or create record through factory_girl association

I am trying to understand the difference between these four methods. I know by default that `==` calls the method `equal?` which returns true when both operands refer to exactly the same object.

`===` by default also calls `==` which calls `equal?`... okay, so if all these three methods are not overridden, then I guess
`===`, `==` and `equal?` do exactly the same thing?

Now comes `eql?`. What does this do (by default)? Does it make a call to the operand&#39;s hash/id? 

Why does Ruby have so many equality signs? Are they supposed to differ in semantics?


What&#39;s the difference between equal?, eql?, ===, and ==?

I was wondering how I would best validate URLs in Rails. I was thinking of using a regular expression, but am not sure if this is the best practice.

And, if I were to use a regex, could someone suggest one to me? I am still new to Regex.

Rails: What&#39;s a good way to validate links (URLs)?

Sometimes I see methods in Ruby that have &quot;?&quot; and &quot;!&quot; at the end of them, e.g:

    name = &quot;sample_string&quot;
    name.reverse
    name.reverse!
    name.is_binary_data?

I was wondering what their purpose is? Are they just syntax sugarcoating?

Content Type	Original Author	Original Content on Stackoverflow
Question	Kir	View Question on Stackoverflow
Solution 1 - Arrays	Dogbert	View Answer on Stackoverflow

Get difference of arrays in Ruby

Arrays Problem Overview

Arrays Solutions

Solution 1 - Arrays

How to write a list to a file with newlines in Python3

How to provide a context configuration for a web application in Tomcat?

Attributions