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6.6 Diversion

In the process of making the HTML files, WML implements a text diversion filter. That bit of jargon means that a section of text can be created in one place in a file, or in a completely separate file, and then included somewhere else within the HTML. This is most helpful with templates, because a template is an HTML file that usually defines the outer HTML (the top, sides, and bottom), and the inner HTML (the page contents) is in a separate file.

This is one syntax to create a diversion:

..DIVERSION>>This is the diversion text<<.. 

The marker ..DIVERSION>> begins the text. The name DIVERSION is all uppercase by convention. The diversion does not have to be named DIVERSION; it can be named anything you want as long as the name begins with an alpha and is followed by zero or more alphas, digits, or underscores, upper-or lowercase. The text in the diversion continues until the end-of-diversion marker <<.. is found.

To use the diversion later (or even before its definition) use this:

<<DIVERSION>> 

This causes the text in the definition to be included at this point.

An example can be found in /var/www/html/wml/diversion.wml:

..NAME>>John Doe<<.. 
Hello <<NAME>>! 
<br> 
Here is my message: <<MSG>> 
..MSG>> 
WML is cool! 
<<.. 

The example starts with a diversion definition for NAME, "John Doe." The next line uses the diversion <<NAME>> in the text:

Hello <<NAME>>! 

This line becomes this, after WML is finished processing:

Hello John Doe! 

The definition of NAME comes before its use. That's fine. The next line, however, uses a diversion not yet defined:

Here is my message: <<MSG>> 

The diversion for MSG is defined after it is used. That's kosherbecause WML is a multipass process, the definition can be before or after. This definition:

..MSG>> 
WML is cool! 
<<.. 

spans multiple lines. That's fine tooyou are free to add whitespace as needed or desired.

To build the HTML, make the WML in the usual fashion:

$ wmk diversion.wml 
wml -n -o diversionl diversion.wml 

The resulting HTML file is:

Hello John Doe! 
<br> 
Here is my message: 
WML is cool! 

If you want to see this example, check out http://localhost/wml/diversionl or www.opensourcewebbook.com/wml/diversionl.

There are other diversion syntaxes as well. One such syntax is:

# create the diversion to use later 
{#NAME#: 
John Doe 
:##} 
# use the diversion 
My name is: {#NAME#}! 

This is another syntax, which requires the use of wml::std::tags:

#use wml::std::tags 
<divert NAME>John Doe</divert> 
My name is: <dump NAME>! 

We most often use the ..NAME>> ... <<.. syntax, but on occasion we use the <divert NAME> ... </divert> syntaxTMTOWTDI (in WML as well as in Perl and most things LAMP).