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Re: regular expressions

• To: xml-dev@l...
• Subject: Re: regular expressions
• From: Rick Jelliffe <ricko@a...>
• Date: Fri, 30 Jan 2004 17:54:17 +1100
• In-reply-to: <200401292002.i0TK2kHX080757@a...>
• References: <200401292002.i0TK2kHX080757@a...>
• User-agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.3.1) Gecko/20030428

David Tolpin wrote:

>Some schema languages use string regular expressions to check lexical space of 
>attributes and character data. The regex strings often become uncomprehensible,
>such as
>
>(([a-zA-Z][0-9a-zA-Z+\-\.]*:)?/{0,2}[0-9a-zA-Z;/?:@&=+$\.\-_!~*'()%]+)?(#[0-9a-zA-Z;/?:@&=+$\.\-_!~*'()%]+)?
>
>for any URI. 
>
>Providing a structured syntax, similar to that for XML, would help reading and debugging
>them, for example,
>
>    s-pattern="""
>      comment = "\(([^\(\)\\]|\\.)*\)"
>      atom = "[a-zA-Z0-9!#$%&'*+\-/=?\^_`{|}~]+"
>      atoms = atom "(\." atom ")*"
>      person = "\"([^\"\\]|\\.)*\""
>      location = "\[([^\[\]\\]|\\.)*\]"
>      local-part = "(" atoms "|" person ")"
>      domain = "(" atoms "|" location ")"
>      start = "(" comment " )?" local-part "@" domain "( " comment ")?"
>    """
>
>instead of 
>
>    pattern=
>      "(\(([^\(\)\\]|\\.)*\) )?"
>    ~ """([a-zA-Z0-9!#$%&'*+\-/=?\^_`{|}~]+(\.[a-zA-Z0-9!#$%&'*+\-/=?\^_`{|}~]+)*|"([^"\\]|\\.)*")"""
>    ~ "@" 
>    ~ "([a-zA-Z0-9!#$%&'*+\-/=?\^_`{|}~]+(\.[a-zA-Z0-9!#$%&'*+\-/=?\^_`{|}~]+)*|\[([^\[\]\\]|\\.)*\])"
>    ~ "( \(([^\(\)\\]|\\.)*\))?"
>
>Why isn't it done?
> 
>
I always do that for our Java regular expresions:

String  s-pattern="\"";
String        comment = "\(([^\\(\)\\]|\\.)*\)";
String        atom = "[a-zA-Z0-9!#$%&'*+\-/=?\^_`{|}~]+";
String        atoms = atom + "(\."  + atom  + ")*";
String        person = "\"([^\"\\]|\\.)*\"";
String        location = "\[([^\[\]\\]|\\.)*\]";
String        local-part = "("  + atoms  + "|" +  person  + ")";
String        domain = "("  + atoms  + "|"  + location  + ")";
String        start = "("  +  comment  + " )?"  + local-part  + "@"  + domain  + "( "  + comment +  ")?";

or whatever. Crazy not to IMHO.

Cheers
Rick Jelliffe

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