Saturday, 9 March 2013

Samsung Series 9

Since June 2012 my primary machine has been the Samsung Series 9. It is a lovely machine to use. Great keyboard. Fabulous screen. Possibly, a too sensitive a track pad. I love the keyboard backlight, particularly if I want to do late night internet surfing! That being said, it was not the easiest of machines to build. My distribution of choice is Linux Mint Debian Edition. It is a rolling edition so at least I will not ever need to do a re-installation! In theory at least. So far so good.
There is way to much to cover in this blog about what I did to configure this machine. Instead please read my Google Drive page about this, here.

Monday, 11 February 2013

I'm Learning JavaScript!

I’ve finally learning about JavaScript after listening to the Google TechTalk, Doug Crockford: JavaScript: The Good Parts. Here are my first couple of test scripts. I’m using Rhino for runtime and JSLint (obviously) to check the code.

Through these code examples I learnt a lot, about the tools, the language and how to integrate it to do useful stuff. It is early days, but I can see JavaScript being a valuable instrument in my tool box!

Example 1 - Random Digits

Here is a simple command line script to produce random numbers from 0 to 9. The first two lines are pragmas passed to JSLint.


/*jslint indent: 4, maxlen: 80, rhino: true */
/*global java*/


// returns a semi-random digit between 0 and 9
function getRandomDigit() {
   
'use strict';
   
return Math.round(Math.random() * 9);}


// example using array
var digitName = (function () {
   
'use strict';
   
var names = ['zero', 'one', 'two', 'three', 'four',
       
'five', 'six', 'seven', 'eight', 'nine'];
   
return function (n) {
       
return names[n];
   
};
}());

// example using associative array
var getDigitName = (function () {
   
'use strict';
   
var names = {0 : 'zero', 1 : 'one', 2 : 'two',
       3 :
'three', 4 : 'four', 5 : 'five',
       6 :
'six', 7 : 'seven', 8 : 'eight',
       9 :
'nine' };
   
return function (n) {
       
return names[n];
   
};
}());

/*
* MAIN
*/
print(
'Printing 10 random digits ...');
var i;
for (i = 0; i < 10; i += 1) {
   
var rd = getRandomDigit();
   print(
'\t' + i + ') ' + rd + ' is ' + getDigitName(rd));
}


Here is an example execution of this script
$ rhino digit.js
Printing 10 random digits ...
0) 0 is zero
1) 6 is six
2) 2 is two
3) 1 is one
4) 3 is three
5) 2 is two
6) 1 is one
7) 6 is six
8) 8 is eight
9) 2 is two

Example 2 - Read an XML Document

Here I am using XPath to process an XML document.
Here is the test input file test.xml.

<?xml version="1.0" encoding="UTF-8"?>
<company>
 <employee id="003">frank</employee>
 <turnover>
   <year id="2011">100000</year>
   <year id="2012">140000</year>
   <year id="2013">200000</year>
 </turnover>
</company>

The script reads the document in three ways

  • query for a specific element meeting an attribute condition
  • show content of all nodes from a specific point
  • show the same, but this time including the attributes

/*jslint indent: 4, maxlen: 80, rhino: true */
/*global java, javax, org*/


// returns a semi-random digit between 0 and 9
function loadXml(fileName) {
   
'use strict';
   
var dbFactory = javax.xml.parsers.DocumentBuilderFactory.newInstance(),
       dBuilder = dbFactory.newDocumentBuilder(),
       xmlFile = java.io.File(fileName),
       xmlDoc = dBuilder.parse(xmlFile);
   xmlDoc.normalizeDocument();
   
return xmlDoc;}


// constructor
function DocumentNodes(xmlDoc) {
   
'use strict';
   
//var my = this;
   
this.xmlDoc = xmlDoc;
   
this.xpFactory = javax.xml.xpath.XPathFactory.newInstance();
   
this.xpath = this.xpFactory.newXPath();
   
// return node set of a specific type for a given expression
   
this.get = function (expression, type) {
       
var xpexpression = this.xpath.compile(expression);
       
return xpexpression.evaluate(this.xmlDoc, type);
   
};
}


/**************************************
* MAIN
**************************************/


// load document
var xmlDoc = loadXml('test.xml');

// read using xpath
var nodes = new DocumentNodes(xmlDoc);var results = nodes.get('/company/turnover/year[@id=2012]',
               javax.xml.xpath.XPathConstants.NODESET);


// show a specific year
var i;for (i = 0; i < results.getLength(); i += 1) {
   
var node = results.item(i).getFirstChild();
   print(
'Year 2012 has turnover of ' + node.getTextContent());
}


// show all years
results = nodes.get(
'/company/turnover/*',
           javax.xml.xpath.XPathConstants.NODESET);

for (i = 0; i < results.getLength(); i += 1) {
   print(results.item(i).getTextContent());

}


// show attributes and value for each year
for (i = 0; i < results.getLength(); i += 1) {
   
if (results.item(i).hasAttributes()) {
       print(results.item(i).getTextContent() +
' has attributes');
       
var attribs = results.item(i).getAttributes();
       
var j;
       
for (j = 0; j < attribs.getLength(); j += 1) {
           
var n = attribs.item(j);
           print(
'\t' + n.getNodeName() + ' = ' + n.getNodeValue());
       
}
   
}
}

And here is the scripts execution

$ rhino loadxml.js
Year 2012 has turnover of 140000
100000
140000
200000
100000 has attributes
id = 2011
140000 has attributes
id = 2012
200000 has attributes
id = 2013