isValidIP

As promised, more regular expression fun. This week we're going to validate IP addresses. An IP address consists of four octets separated by periods. A lazy person might be inclined to use a regular expression of \d{1,3} for each octet, but that would allow numbers larger than 255. A more complex expression is needed: ([1]?\d{1,2}|2[0-4]{1}\d{1}|25[0-5]{1}).

This expression consists of three parts separated by the pipe character "|". The first part, [1]?\d{1,2}, matches numbers between 0 and 199. The second part, 2[0-4]{1}\d{1}, matches numbers between 200 and 249. The third part, 25[0-5]{1}, matches numbers between 250 and 255. We will repeat this pattern four times, once for each octet, and separate with periods.

ASP

1. function isValidIP(ip)
2.     dim regEx
4.     set regEx = new RegExp
6.     with regEx
7.         .IgnoreCase = True
8.         .Global = True
9.         .Pattern = "^([1]?\d{1,2}|2[0-4]{1}\d{1}|25[0-5]{1})(\.([1]?\d{1,2}|2[0-4]{1}\d{1}|25[0-5]{1})){3}$"
10.     end with
12.     if regEx.Test(trim(CStr(ip))) then
13.         isValidIP = true
14.     else
15.         isValidIP = false
16.     end if
18.     set regEx = nothing
19. end function

PHP

1. function isValidIP($ip)
2. {
3.     $pattern = "/^([1]?\d{1,2}|2[0-4]{1}\d{1}|25[0-5]{1})(\.([1]?\d{1,2}|2[0-4]{1}\d{1}|25[0-5]{1})){3}$/";
4.     return (preg_match($pattern, $ip) > 0) ? true : false;
5. }

Next week we're going to build on this pattern to validate something else. I wonder what that could be?

• View ASP implementation on Snipplr
• View PHP implementation on Snipplr

isAlpha(Numeric)

We're going to take a break from math-related functions for a few weeks (yay!) and play with regular expressions. Regular expressions are more powerful and faster than old-fashioned string parsing.

Both ASP and PHP have a function for checking if something is numeric. How about a function for checking if something is alphabetical?

ASP

1. function isAlpha(someString)
2.     dim regEx
4.     set regEx = new RegExp
6.     with regEx
7.         .Global = true
8.         .IgnoreCase = true
9.         .Pattern = "[A-Z\s_]"
10.     end with
12.     if regEx.test(someString) then
13.         isAlpha = true
14.     else
15.         isAlpha = false
16.     end if
18.     set regEx = nothing
19. end function

PHP

1. function is_alpha($someString)
2. {
3.     return (preg_match("/[A-Z\s_]/i", $someString) > 0) ? true : false;
4. }

The test pattern we are using above will allow letters of the alphabet, the underscore character, and whitespace characters. With a small tweak to the test pattern, we can also write a function to check if a string is alphanumeric.

ASP

1. function isAlphaNumeric(someString)
2.     dim regEx
4.     set regEx = new RegExp
6.     with regEx
7.         .Global = true
8.         .IgnoreCase = true
9.         .Pattern = "[\w\s.]"
10.     end with
12.     if regEx.test(someString) then
13.         isAlphaNumeric = true
14.     else
15.         isAlphaNumeric = false
16.     end if
18.     set regEx = nothing
19. end function

PHP

1. function is_alphanumeric($someString)
2. {
3.     return (preg_match("/[\w\s.]/i", $someString) > 0) ? true : false;
4. }

The \w switch in the pattern includes the 26 letters of the alphabet plus the numbers zero through nine.

More regular expression fun next week!

• View ASP implementation for isAlpha on Snipplr
• View PHP implementation for is_alpha on Snipplr
• View ASP implementation for isAlphaNumeric on Snipplr
• View PHP implementation for is_alphanumeric on Snipplr

Fibonacci numbers

The Fibonacci numbers have many applications in computer programming. Today we're going to write a function that returns individual numbers from the Fibonacci sequence.

ASP

1. function fib(x)
2.     dim fibArray()
3.     redim fibArray(x)
5.     fibArray(0) = 0
6.     fibArray(1) = 1
8.     for i = 2 to x
9.         fibArray(i) = fibArray(i - 1) + fibArray(i - 2)
10.     next
12.     fib = fibArray(x)
13. end function

PHP

1. function fib($x)
2. {
3.     $fibArray[0] = 0;
4.     $fibArray[1] = 1;
6.     for($i = 2; $i <= $x; $i++)
7.     {
8.         $fibArray[$i] = $fibArray[$i - 1] + $fibArray[$i - 2];
9.     }
11.     return $fibArray[$x];
12. }

So, for example, fib(8) will return 21, because the Fibonacci sequence is 1, 1, 2, 3, 5, 8, 13, 21, 34, 55...

• View ASP implementation on Snipplr
• View PHP implementation on Snipplr

Fermat numbers

Today we're going to write a function to generate Fermat numbers. This could be useful if you want to write your own pseudo-random number generator.

ASP

1. function fermat(x)
2.     fermat = 2^2^x + 1
3. end function

PHP

1. function fermat($x)
2. {
3.     return 2^2^$x + 1;
4. }

• View ASP implementation on Snipplr
• View PHP implementation on Snipplr