According to the sites faq:

Wolfram|Alpha’s long-term goal is to make all systematic knowledge immediately computable and accessible to everyone. We aim to collect and curate all objective data; implement every known model, method, and algorithm; and make it possible to compute whatever can be computed about anything. Our goal is to build on the achievements of science and other systematization of knowledge to provide a single source that can be relied on by everyone for definitive answers to factual queries.

Conceived by the brilliant Stephen Wolfram, its another feather in his cap after his magnificent Mathematica software.

As an example if you search for “life expectancy male age 40 Finland” the engine will return the following:

Or if you search for “president of Brazil in 1922″:

Or a mathematical query like “3,7,15,31,63,…”, and wolframalpha computes the next terms in the series and also gives the functions for the same:

The other interesting feature of the software engine is that for many queries it computes the information from realtime data. For example if you were to search for ‘moon’ than wolframalpha would give all the details of the same and also such information as the present position in the sky, distance from the earth, etc. You can watch the detailed examples here. Imagine what this kind of information can do in the hands of researchers and scientists. An exponential increase in the present knowledge in all areas of science.

The above example are just the tip of what the engine can do. Imagine a robot linked to the WolframAlpha engine and you can get the picture of where we are heading. We are on our way to building a true Encyclopedia Galactica. Knowledge search will never be the same again. Wish Asimov was here!

c:/> pear install File_SearchReplace

Doing a simple search & replace
The following is an simple example code that searches the file ‘fruits.txt’ and replaces all occurrences of ‘apples’ with ‘oranges’. The getNumOccurences function returns the total number of replaced strings in the file.

<?php
 
include 'File/SearchReplace.php' ;
 
$files_to_search = array("fruits.txt") ;
$search_string  = "apples";
$replace_string = "oranges";
 
$snr = new File_SearchReplace($search_string,
                              $replace_string,
                              $files_to_search,
                              '', // directorie(s) to search
                              false) ;
 
$snr->doSearch();
 
echo "The number of replaces done : " . $snr->getNumOccurences();
 
?>

The fourth option in the File_SearchReplace specifies a optional directory name to search. If the directory name is empty than the files will be searched in the current directory or in the respective path if a path is also included with the filename. Following is an example if you want to search all files in the directory ‘nature/fruits’.

<?php
 
include 'File/SearchReplace.php' ;
 
$files_to_search = array();
$direc_to_search = array('nature/fruits/');
 
$search_string  = "apples";
$replace_string = "oranges";
 
$snr = new File_SearchReplace($search_string,
                              $replace_string,
                              $files_to_search,
                              $direc_to_search, // directory to search
                              true) ; // 'true' to search subdirectories
 
$snr->doSearch();
 
echo "The number of replaces done : " . $snr->getNumOccurences();
 
?>

All the four starting options of File_SearchReplace are of mixed type; i.e they take a string or an array of strings as their options. For example in the following all occurrences of ‘apples’ will be replaced by ‘oranges’ and that of ‘pears’ by ‘grapes’.

<?php
 
include 'File/SearchReplace.php' ;
 
$files_to_search = array();
$direc_to_search = array('nature/fruits/');
 
$search_string  = array('apples', 'pears');
$replace_string = array('oranges', 'grapes');
 
$snr = new File_SearchReplace($search_string,
                              $replace_string,
                              $files_to_search,
                              $direc_to_search,
                              true) ;
$snr->doSearch();
 
echo "The number of replaces done : " . $snr->getNumOccurences();
 
?>

You don’t have to create a new instance everytime you need a new search, you can set the various parameters through the interface provided by the File_SearchReplace class as shown below.

<?php
 
include 'File/SearchReplace.php' ;
 
$files_to_search = array();
$direc_to_search = array('nature/fruits/');
 
$search_string  = array('apples', 'pears');
$replace_string = array('oranges', 'grapes');
 
$snr = new File_SearchReplace($search_string,
                              $replace_string,
                              $files_to_search,
                              $direc_to_search,
                              true) ;
$snr->doSearch();
 
echo "The number of replaces done : " . $snr->getNumOccurences();
 
/* Start a new search */
 
$snr->setFind( "oranges") ;
$snr->setReplace( "berries") ;
$snr->doSearch();
 
echo "The number of replaces done : " . $snr->getNumOccurences();
 
?>

Regular Expression search
You can also use a regular expression in a search string, but before that we must specify what kind of search is required with the ‘setSearchFunction’ as shown below. The following example replaces all occurrences of ‘color’ or ‘colour’ with the capital ‘COLOR’.

<?php
 
include 'File/SearchReplace.php' ;
 
$files_to_search = array();
$direc_to_search = array('test/graphics/');
 
$search_string  = '/col(o|ou)r/';
$replace_string = 'COLOR';
 
$snr = new File_SearchReplace($search_string,
                              $replace_string,
                              $files_to_search,
                              $direc_to_search,
                              true) ;
 
$snr->setSearchFunction("preg");
$snr->doSearch();
 
echo "The number of replaces done : " . $snr->getNumOccurences();
 
?>

The setSearchFunction takes one of the following four options:

normal – default
quick – use str_replace()
preg – use preg_replace()
ereg – use ereg_replace()

More information on this options can be found here.

In conclusion
The package can be quite useful when you want to replace large quantities of text programatically. As it works on plain strings and regular expressions, its can be quite a handy tool in many occasions.

A stemming algorithm lets you reduce each English input word to its basic root or stem (e.g. ‘walking’ to ‘walk’) so that variations on a word (‘walks’, ‘walked’, ‘walking’) are considered equivalent when searching. This stems can than be used in a search query rather than the original words, which generally (but not always) results in more relevant search results. The main use of stemming is in keyword indexing for search. For example if you have a article or document titled ‘blogging tips for late workers‘ and you run it through the algorithm you will get a list of stems for the title – blog, tip, late, worker; under which you can than index the article or document.

The original paper on the algorithm by Martin Porter, generally known as the Porter Stemming algorithm can be found here. The Porter Stemming algorithm essentially works by stripping suffixes from a word by using certain rules.

There are many implementation of the algorithm in various languages, so we will use one of those for our job. We will use a PHP5 implementation by Richard Heyes which can be downloaded from here.

Below is an example of the use of the class, which is as simple as it can ever get.

<?php
 
    require_once 'libs/PorterStemmer.php';
 
    $word_to_stem = 'walking';
    $stem = PorterStemmer::Stem($word_to_stem);
    echo $stem; // returns 'walk'
 
?>

The following example will create a list of stem words from a article title, also removing stop words from the list if any.

<?php
 
    /*Create a list of stem words for a article title */
 
 
    require_once 'libs/PorterStemmer.php';
 
    $title = "blogging tips for late workers";
 
    /* Stop words to filter out. Not comprehensive though  */
    $stop_words = array("the", "and", "a", "to", "of", "in", "i", "is",
                         "that", "it", "on", "you", "this", "for", "but",
                         "with", "are", "have", "be", "at", "or", "as",
                         "was", "so", "if", "out", "not");
 
    $words = explode(" ", $title);
 
    foreach($words as $word) {
        $stem = PorterStemmer::Stem($word);
 
        /* Remove stop words */
        if(!in_array($stem, $stop_words)) {
            $stem_words[] = $stem;
        }
    }
 
    print_r($stem_words);
 
?>

Which will return the following:

Array
(
    [0] => blog
    [1] => tip
    [2] => late
    [3] => worker
)

The algorithm is basically useful when you want to index documents or extend search for morphologically related words. Although it sometimes gives amusing results, it can be quite helpful at appropriate times.