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

AM/PM

To those of you who have been bored by the recent string of math-related articles, I apologize. I still have a lot of math-related functions to share with you, but I do have other things to share with you as well, such as validation functions, string functions, and datetime functions. This week we'll take a look at one of those datetime functions.

In ASP, time values are normally in the format HH:MM:SS followed by AM or PM. Quite often, we don't want to include the seconds portion, so we extract the hours and minutes using the Hour() and Minute() functions respectively. Unfortunately, there is no quick function for extracting the AM/PM. Let's do something about that right now.

1. function ampm(someTime)
2.     if hour(someTime) < 12 then
3.         ampm = "AM"
4.     else
5.         ampm = "PM"
6.     end if
7. end function

Now we can do stuff like this:
Hour(someTime) & ":" & Minute(someTime) & " " & ampm(someTime)

Those of you who are PHP programmers are hopefully aware that the same result can be achieved in PHP using the built-in date() function and specifying the letter A or a in the format string for uppercase or lowercase respectively:
date("g:i A", $timestamp)

View this code on Snipplr

Factorial

This week we're going to delve into some discrete math, starting with factorial. The factorial of a number is the product of that number and all the numbers smaller than it. For example, the factorial of 3 is 1 x 2 x 3 = 6.

ASP

1. function factorial(x)
2.     dim result
4.     result = 1
6.     if x > 1 then
7.         for i = 2 to x
8.             result = result * i
9.         next
10.     end if
12.     factorial = result
13. end function

PHP

1. function factorial($x)
2. {
3.     $result = 1;
5.     if ($x > 1)
6.     {
7.         for ($i = 2; $i <= $x; $i++)
8.         {
9.             $result *= $i;
10.         }
11.     }
13.     return $result;
14. }

Now that we have a function for factorial, we can also do combinatorial. Combinatorial tells us the number of combinations, without regard to order, of y items that can be made from a pool of x items.

ASP

1. function combinatorial(x, y)
2.     if (x >= y) and (y > 0) then
3.         combinatorial = factorial(x) / factorial(y) / factorial(x - y)
4.     else
5.         combinatorial = 0
6.     end if
7. end function

PHP

1. function combinatorial($x, $y)
2. {
3.     return (($x >= $y) && ($y > 0)) ? factorial($x) / factorial($y) / factorial($x - $y) : 0;
4. }

We can also get the number of permutations of y items that can be made from a pool of x items.

ASP

1. function permutations(x, y)
2.     permutations = factorial(x) / factorial(x - y)
3. end function

PHP

1. function permutations($x, $y)
2. {
3.     return factorial($x) / factorial($x - $y);
4. }

• ASP implementation on Snipplr
• PHP implementation on Snipplr

Pythagorean Theorem

When you're dealing with right-angled triangles, trigonometry is not required to calculate the length of the hypotenuse. Our PHP programmers friends have a function called hypot() which solves for c in the equation: a^2 + b^2 = c^2

1. function hypot(a, b)
2.     hypot = sqr(a^2 + b^2)
3. end function

Using the classic 3-4-5 triangle as an example, for a = 3 and b = 4, the function will return 5.

View this code on Snipplr