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