str_repeat

This week we're duplicating another string function from PHP: str_repeat().

ASP

1. function str_repeat(input, multiplier)
2.     dim output
4.     output = ""
6.     for i = 1 to multiplier
7.         output = output & input
8.     next
10.     str_repeat = output
11. end function

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str_pad

PHP has a very useful function called str_pad(). It allows you to ensure that a string will conform to a specific length by adding characters of your choice on the end of your choice. A good practical example is when you want a number with leading zeros. ASP doesn't have an equivalent function out of the box, but we're going to write one today; as usual, we'll follow the same syntax to make it easy for those who are already familiar with PHP.

ASP

1. Const STR_PAD_LEFT = "LEFT"
2. Const STR_PAD_RIGHT = "RIGHT"
3. Const STR_PAD_BOTH = "BOTH"
5. ' Pad a string to a certain length with another string.
6. function str_pad(input, pad_length, pad_string, pad_type)
7.     dim output
8.     dim difference
10.     output = ""
11.     difference = pad_length - len(input)
13.     if difference > 0 then
14.         select case ucase(pad_type)
15.         case "LEFT"
16.             for i = 1 to difference step len(pad_string)
17.                 output = output & pad_string
18.             next
20.             output = right(output & input, pad_length)
21.         case "BOTH"
22.             output = input
24.             for i = 1 to difference step len(pad_string) * 2
25.                 output = pad_string & output & pad_string
26.             next
28.             ' Not sure if it will step far enough when difference is an odd number, so this next block is just in case.
29.             if len(output) < pad_length then
30.                 output = output & pad_string
31.             end if
33.             output = left(output, pad_length)
34.         case else
35.             for i = 1 to difference step len(pad_string)
36.                 output = output & pad_string
37.             next
39.             output = left(input & output, pad_length)
40.         end select
41.     else
42.         output = input
43.     end if
45.     str_pad = output
46. end function

Thinking back to my days as a web developer, this was probably the most reused function out of all I'd ever written.

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Roman Numerals, Part 3

Back in March, we wrote a function to turn an arabic number into a Roman numeral. That function had a limitation of numbers smaller than 5000. There are ways of writing Roman numerals larger than 5000, but they are not as well accepted by purists because they evolved during later time periods. Out of respect for the purists, this new function will hinge on the old one, rather than replace it.

In the system we will be using, a bar is placed over the numeral to indicate that it is multipled by 1000:

• V = 5000
• X = 10,000
• L = 50,000
• C = 100,000
• D = 500,000
• M = 1 million

Since there are no Unicode characters for this purpose, we will have to cheat a little bit by using some HTML and CSS.

ASP

1. function bigroman(ByVal arabic)
2.     dim thousands
4.     thousands = Array("", "M", "MM", "MMM", "M(V)", "(V)", "(V)M", "(V)MM", "(V)MMM", "M(X)")
6.     if arabic >= 10000 then
7.         bigroman = "(" & roman((arabic - (arabic mod 10000)) / 1000) & ")"
8.         arabic = arabic mod 10000
9.     end if
11.     bigroman = bigroman & thousands((arabic - (arabic mod 1000)) / 1000)
12.     arabic = arabic mod 1000
13.     bigroman = bigroman & roman(arabic)
15.     ' Convert parentheses to <span> tags.
16.     bigroman = replace(bigroman, "(", "<span style=""text-decoration: overline"">")
17.     bigroman = replace(bigroman, ")", "</span>")
18. end function

PHP

1. function bigroman($arabic)
2. {
3.     $thousands = Array("", "M", "MM", "MMM", "M(V)", "(V)", "(V)M", "(V)MM", "(V)MMM", "M(X)");
5.     if ($arabic >= 10000)
6.     {
7.         $bigroman = "(" . roman(($arabic - fmod($arabic, 10000)) / 1000) . ")";
8.         $arabic = fmod($arabic, 10000);
9.     }
11.     $bigroman .= $thousands[($arabic - fmod($arabic, 1000)) / 1000];
12.     $arabic = fmod($arabic, 1000);
13.     $bigroman .= roman($arabic);
15.     // Convert parentheses to <span> tags.
16.     $bigroman = str_replace("(", "<span style=""text-decoration: overline"">", $bigroman);
17.     $bigroman = str_replace(")", "</span>", $bigroman);
19.     return $bigroman;
20. }

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isValidPostCode

In this final installment of the postal code trilogy, we turn our attention to the United Kingdom. Postal codes in the UK are called postcodes. They are similar to postal codes in Canada in that they contain both letters and numbers, but unlike Canadian postal codes, they are variable in length.

A postcode can have any of the following formats:

• A9 9AA
• A99 9AA
• A9A 9AA
• AA9 9AA
• AA99 9AA
• AA9A 9AA

To match all of these formats, we'll use the following regular expression: [A-PR-UWYZ]([0-9]{1,2}|([A-HK-Y][0-9]|[A-HK-Y][0-9]([0-9]|[ABEHMNPRV-Y]))|[0-9][A-HJKS-UW])\ [0-9][ABD-HJLNP-UW-Z]{2}. You may notice that, like Canadian postal codes, certain letters are only allowed in certain positions, or not at all.

There are also a few special cases that are valid postcodes but deviate from the regular format:

• Girobank - (GIR\ 0AA)
• Father Christmas - (SAN\ TA1)
• British Forces Post Office - (BFPO\ (C\/O\ )?[0-9]{1,4})
• Overseas territories - ((ASCN|BBND|[BFS]IQQ|PCRN|STHL|TDCU|TKCA)\ 1ZZ)

ASP

1. function isValidPostCode(postCode)
2.     dim regEx
4.     set regEx = new RegExp
6.     with regEx
7.         .IgnoreCase = true
8.         .Global = true
9.         .Pattern = "^([A-PR-UWYZ]([0-9]{1,2}|([A-HK-Y][0-9]|[A-HK-Y][0-9]([0-9]|[ABEHMNPRV-Y]))|[0-9][A-HJKS-UW])\ [0-9][ABD-HJLNP-UW-Z]{2}|(GIR\ 0AA)|(SAN\ TA1)|(BFPO\ (C\/O\ )?[0-9]{1,4})|((ASCN|BBND|[BFS]IQQ|PCRN|STHL|TDCU|TKCA)\ 1ZZ))$"
10.     end with
12.     if regEx.Test(trim(CStr(postCode))) then
13.         isValidPostCode = true
14.     else
15.         isValidPostCode = false
16.     end if
18.     set regEx = nothing
19. end function

PHP

1. function isValidPostCode($postCode)
2. {
3.     $pattern = "/^([A-PR-UWYZ]([0-9]{1,2}|([A-HK-Y][0-9]|[A-HK-Y][0-9]([0-9]|[ABEHMNPRV-Y]))|[0-9][A-HJKS-UW])\ [0-9][ABD-HJLNP-UW-Z]{2}|(GIR\ 0AA)|(SAN\ TA1)|(BFPO\ (C\/O\ )?[0-9]{1,4})|((ASCN|BBND|[BFS]IQQ|PCRN|STHL|TDCU|TKCA)\ 1ZZ))$/i";
4.     return (preg_match($pattern, trim($postCode)) > 0) ? true : false;
5. }

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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. }

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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.

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