Vista - regular expressions - why are they so hard to compose and decipher?

Except for a few concepts like anchoring the match to the beginning and ending
of a target using ^ and $ I have the hardest time internalizing the syntax of
regular expressions.

The opposite is true of wildcards. I am completely comfortable with them. I
don't know if that's because I encountered them first, or that they are so
simple that there are not combinations of characters to learn.

It all seems "learned by rote" to me. It may be the escape sequences embedded
in them that makes it seem that they are more complex that they really are.

I guess I need to learn a process of first resolving the escaped characters into
a special notation that uses one symbol per escaped character, and then seeing
what patterns emerge. I'm lost in the slashes!

I feel with regular expressions like I feel with the game of Chess. I know how
all the pieces move, and how the game is played, but have no feeling of comfort
that I play well (and plenty of experiences that prove it to be true that I play
poorly).

- Larry

Thanks to Don Jones for this remarkably easy to follow starter on PowerShell regex

http://207.46.16.252/en-us/magazine/...owershell.aspx

I guess I missed out on some "recent" regex expansion since I've never coded
with Perl.

http://en.wikipedia.org/wiki/Regular...racter_classes

- Larry Weiss

Larry__Weiss wrote:

Also,
http://www.johndcook.com/regex.html

is helpful to learn just how alike Perl and PowerShell are wrt regex.

- Larry

Larry__Weiss wrote:

On Sep 3, 12:56*pm, Larry__Weiss <l...@xxxxxx> wrote:Regular expressions ARE more complicated than wildcards, but they can
do a whole lot more. There are more than the items listed below, like
zero-width lookahead and lookbehind assertions, but this little cheat
sheet will work for you 99% of the time.

Most regex tokens fall into one of four categories:

1. What kind of character is it?
--------------------------------

[] - Any of the characters inside the brackets will match, use the
dash to indicate a range.
Examples: [a-z] will match any letter.
[aeiou] will match any vowel
\w - "word" characters. Basically matches [a-z0-9_]
\s - "whitespace" characters. matches spaces, tabs, etc.
\d - any digit. Basically matches [0-9]
\t - a tab character
.. - any character


2. How many characters? (the below appear after the character class)
-----------------------

{x} - Matches x number of characters
{x, y} - Matches minimum x number of characters, maximum y characters
Examples: \d{4} matches 4 digits
* - Matches ZERO or more of the character (as many as possible)
+ - Matches ONE or more of the character (as many as possible)
*? - Matches ZERO or more characters (as few as possible)
+? - Matches ONE or more characters (as few as possible)


3. Where is the character?
--------------------------

\b - matches a word boundary, without actually absorbing any
characters
^ - matches the beginning of a string
$ - matches the end of a strong


4. Grouping
-----------

() - Any characters between the parentheses will be their own group.
Check $matches after using -match to see the groups.
| - A pipe character is the OR character
Example: (one|two) will match the word "one" or the word "two"

Super! Like those "as many as possible" and "as few as possible" descriptions.

- Larry

tojo2000 wrote: