isValidPostalCode

This week we're turning our attention to my own country, Canada, and writing a function to validate postal codes. Unlike a ZIP code, a postal code contains letters too; the format is A1A 1A1. The simplest regular expression to validate this would be:

^[A-Z]{1}[\d]{1}[A-Z]{1}[ ]?[\d]{1}[A-Z]{1}[\d]{1}$

But not all letters are used, and some letters can only appear in certain positions. Taking this into account gives us a slightly more complex pattern of:

^[ABCEGHJ-NPRSTVXY]{1}[0-9]{1}[ABCEGHJ-NPRSTV-Z]{1}[ ]?[0-9]{1}[ABCEGHJ-NPRSTV-Z]{1}[0-9]{1}$

But I want to take this a step further and check the validity of the combination of the first three characters. The postal code C2B 4S3 has a valid format, but the code itself is not valid because there is no C2B postal area. I also want to check the postal code against the province to ensure that they match.

The full source code is too long to post here, but is available in its entirety from Snipplr in the language of your choice:

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

Alternatively, if you wanted the extended validation, but didn't care about the province matching, you could combine everything into one gigantic regular expression:

^(A(0[ABCEGHJ-NPR]|1[ABCEGHK-NSV-Y]|2[ABHNV]|5[A]|8[A])|B(0[CEHJ-NPRSTVW]|1[ABCEGHJ-NPRSTV-Y]|2[ABCEGHJNRSTV-Z]|3[ABEGHJ-NPRSTVZ]|4[ABCEGHNPRV]|5[A]|6[L]|9[A])|C(0[AB]|1[ABCEN])|E(1[ABCEGHJNVWX]|2[AEGHJ-NPRSV]|3[ABCELNVYZ]|4[ABCEGHJ-NPRSTV-Z]|5[ABCEGHJ-NPRSTV]|6[ABCEGHJKL]|7[ABCEGHJ-NP]|8[ABCEGJ-NPRST]|9[ABCEGH])|G(0[ACEGHJ-NPRSTV-Z]|1[ABCEGHJ-NPRSTV-Y]|2[ABCEGJ-N]|3[ABCEGHJ-NZ]|4[ARSTVWXZ]|5[ABCHJLMNRTVXYZ]|6[ABCEGHJKLPRSTVWXZ]|7[ABGHJKNPSTXYZ]|8[ABCEGHJ-NPTVWYZ]|9[ABCHNPRTX])|H(0[HM]|1[ABCEGHJ-NPRSTV-Z]|2[ABCEGHJ-NPRSTV-Z]|3[ABCEGHJ-NPRSTV-Z]|4[ABCEGHJ-NPRSTV-Z]|5[AB]|7[ABCEGHJ-NPRSTV-Y]|8[NPRSTYZ]|9[ABCEGHJKPRSWX])|J(0[ABCEGHJ-NPRSTV-Z]|1[ACEGHJ-NRSTXZ]|2[ABCEGHJ-NRSTWXY]|3[ABEGHLMNPRTVXYZ]|4[BGHJ-NPRSTV-Z]|5[ABCJ-MRTV-Z]|6[AEJKNRSTVWYXZ]|7[ABCEGHJ-NPRTV-Z]|8[ABCEGHLMNPRTVXYZ]|9[ABEHJLNTVXYZ])|K(0[ABCEGHJ-M]|1[ABCEGHJ-NPRSTV-Z]|2[ABCEGHJ-MPRSTVW]|4[ABCKMPR]|6[AHJKTV]|7[ACGHK-NPRSV]|8[ABHNPRV]|9[AHJKLV])|L(0[[ABCEGHJ-NPRS]]|1[ABCEGHJ-NPRSTV-Z]|2[AEGHJMNPRSTVW]|3[BCKMPRSTVXYZ]|4[ABCEGHJ-NPRSTV-Z]|5[ABCEGHJ-NPRSTVW]|6[ABCEGHJ-MPRSTV-Z]|7[ABCEGJ-NPRST]|8[EGHJ-NPRSTVW]|9[ABCGHK-NPRSTVWYZ])|M(1[BCEGHJ-NPRSTVWX]|2[HJ-NPR]|3[ABCHJ-N]|4[ABCEGHJ-NPRSTV-Y]|5[ABCEGHJ-NPRSTVWX]|6[ABCEGHJ-NPRS]|7[AY]|8[V-Z]|9[ABCLMNPRVW])|N(0[ABCEGHJ-NPR]|1[ACEGHKLMPRST]|2[ABCEGHJ-NPRTVZ]|3[ABCEHLPRSTVWY]|4[BGKLNSTVWXZ]|5[ACHLPRV-Z]|6[ABCEGHJ-NP]|7[AGLMSTVWX]|8[AHMNPRSTV-Y]|9[ABCEGHJKVY])|P(0[ABCEGHJ-NPRSTV-Y]|1[ABCHLP]|2[ABN]|3[ABCEGLNPY]|4[NPR]|5[AEN]|6[ABC]|7[ABCEGJKL]|8[NT]|9[AN])|R(0[ABCEGHJ-M]|1[ABN]|2[CEGHJ-NPRV-Y]|3[ABCEGHJ-NPRSTV-Y]|4[AHJKL]|5[AGH]|6[MW]|7[ABCN]|8[AN]|9[A])|S(0[ACEGHJ-NP]|2[V]|3[N]|4[AHLNPRSTV-Z]|6[HJKVWX]|7[HJ-NPRSTVW]|9[AHVX])|T(0[ABCEGHJ-MPV]|1[ABCGHJ-MPRSV-Y]|2[ABCEGHJ-NPRSTV-Z]|3[ABCEGHJ-NPRZ]|4[ABCEGHJLNPRSTVX]|5[ABCEGHJ-NPRSTV-Z]|6[ABCEGHJ-NPRSTVWX]|7[AENPSVXYZ]|8[ABCEGHLNRSVWX]|9[ACEGHJKMNSVWX])|V(0[ABCEGHJ-NPRSTVWX]|1[ABCEGHJ-NPRSTV-Z]|2[ABCEGHJ-NPRSTV-Z]|3[ABCEGHJ-NRSTV-Y]|4[ABCEGK-NPRSTVWXZ]|5[ABCEGHJ-NPRSTV-Z]|6[ABCEGHJ-NPRSTV-Z]|7[ABCEGHJ-NPRSTV-Y]|8[ABCGJ-NPRSTV-Z]|9[ABCEGHJ-NPRSTV-Z])|X(0[ABCGX]|1[A])|Y(0[AB]|1[A]))[ ]?[0-9]{1}[ABCEGHJ-NPRSTV-Z]{1}[0-9]{1}$

isValidZipCode

Another week, another validation function. Last week was a little long, so this week we'll do a bit shorter one: validating a United States ZIP code. The pattern is simple enough that I don't think an explanation is warranted.

ASP

1. function isValidZIPCode(zipCode)
2.     dim regEx
4.     set regEx = new RegExp
6.     with regEx
7.         .IgnoreCase = True
8.         .Global = True
9.         .Pattern = "^[0-9]{5}(-[0-9]{4})?$"
10.     end with
12.     if regEx.Test(trim(CStr(zipCode))) then
13.         isValidZipCode = True
14.     else
15.         isValidZipCode = False
16.     end if
18.     set regEx = nothing
19. end function

PHP

1. function isValidZIPCode($zipCode)
2. {
3.     return (preg_match("/^[0-9]{5}(-[0-9]{4})?$/i", trim($zipCode)) > 0) ? true : false;
4. }

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

isValidEmail

This week we're going to build on the regular expression we wrote last week to validate e-mail addresses. What do IP addresses have to do with e-mail addresses? Just like domain names map to IP addresses, so also the domain part of an e-mail address can be substituted with an IP address, so instead of person@example.com you could have person@192.168.1.1

ASP

1. function isValidEmail(email)
2.     dim regEx
3.     dim result
5.     set regEx = new RegExp
7.     with regEx
8.         .IgnoreCase = True
9.         .Global = True
10.         .Pattern = "^[^@]{1,64}@[^@]{1,255}$"
11.     end with
13.     result = false
15.     ' Test length.
16.     if regEx.Test(email) then
17.         regEx.Pattern = "^((([\w\+\-]+)(\.[\w\+\-]+)*)|(\"[^(\\|\")]{0,62}\"))@(([a-zA-Z0-9\-]+\.)+([a-zA-Z0-9]{2,})|\[?([1]?\d{1,2}|2[0-4]{1}\d{1}|25[0-5]{1})(\.([1]?\d{1,2}|2[0-4]{1}\d{1}|25[0-5]{1})){3}\]?)$"
19.         ' Test syntax.
20.         if regEx.Test(email) then
21.             result = true
22.         end if
23.     end if
25.     isValidEmail = result
26.     set regEx = nothing
27. end function

PHP

1. function isValidEmail($email)
2. {
3.     $lengthPattern = "/^[^@]{1,64}@[^@]{1,255}$/";
4.     $syntaxPattern = "/^((([\w\+\-]+)(\.[\w\+\-]+)*)|(\"[^(\\|\")]{0,62}\"))@(([a-zA-Z0-9\-]+\.)+([a-zA-Z0-9]{2,})|\[?([1]?\d{1,2}|2[0-4]{1}\d{1}|25[0-5]{1})(\.([1]?\d{1,2}|2[0-4]{1}\d{1}|25[0-5]{1})){3}\]?)$/";
5.     return ((preg_match($lengthPattern, $email) > 0) && (preg_match($syntaxPattern, $email) > 0)) ? true : false;
6. }

The validation is broken down into two steps: checking the length of each part, and checking the syntax of each part.

^[^@]{1,64}@[^@]{1,255}$

The part before the @ symbol is called the local part, and cannot exceed 64 characters. The part after the @ symbol is called the domain part, and cannot exceed 255 characters.

^((([\w\+\-]+)(\.[\w\+\-]+)*)|(\"[^(\\|\")]{0,62}\"))@(([a-zA-Z0-9\-]+\.)+([a-zA-Z0-9]{2,})|\[?([1]?\d{1,2}|2[0-4]{1}\d{1}|25[0-5]{1})(\.([1]?\d{1,2}|2[0-4]{1}\d{1}|25[0-5]{1})){3}\]?)$

In the check for syntax, the local part is validated by ((([\w\+\-]+)(\.[\w\+\-]+)*)|(\"[^(\\|\")]{0,62}\")). This is actually two patterns separated by the pipe character. The first, (([\w\+\-]+)(\.[\w\+\-]+)*), allows letters, numbers, the plus sign, and the hyphen (or minus sign if you prefer). It also allows periods, but not as the first or last character. The second, (\"[^(\\|\")]{0,62}\"), allows just about anything, provided the local part is enclosed in quotation marks (which is valid, but you'll probably never encounter it).

The domain part is validated by (([a-zA-Z0-9\-]+\.)+([a-zA-Z0-9]{2,})|\[?([1]?\d{1,2}|2[0-4]{1}\d{1}|25[0-5]{1})(\.([1]?\d{1,2}|2[0-4]{1}\d{1}|25[0-5]{1})){3}\]?). Once again, this is two different patterns separated by the pipe character. The second pattern is our IP address checker from last week with optional enclosure in square brackets. The first pattern, ([a-zA-Z0-9\-]+\.)+([a-zA-Z0-9]{2,}), allows a slightly smaller range of characters (no plus signs or underscores), any number of subdomains, and a top-level domain of at least 2 characters (the minimum). Some regular expressions will impose a maximum of six characters on the top-level domain (the longest at the moment is .museum), but that wouldn't allow for longer top-level domains that could be created in the future.

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

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