Re: [xsl] Re: Capturing/testing results of a boolean expression.

[Wendell Piez <wapiez at mulberrytech dot com>]

Ed,

At 05:59 PM 8/2/2002, you wrote:
> Maybe details are called for, because as I gnaw at this problem and read
> archives I realize the trick might be to establish an expression which
> returns a "boolean" as opposed to an expression which returns a
> "results-tree-fragment".
Quite right. This is a tricky subtlety in declaring variables, that these 
aren't the same thing.

> I have a variable which will have a string value.  I wish to compare
> that string value to another string value (which happens to be a literal
> value).  I've done this directly in a xsl:if or xsl:when before, but now
> I'm trying to capture the results of the expression in a variable.
>
> <xsl:variable name="X" ..../>
>
> <xsl:variable name="flag" select="$X = 'literal-string-value'" />
>
> Is there a way to do this that returns a 'boolean' and not a
> 'results-tree-fragment'?
The way you gave should do precisely that. The select="$X = 
'literal-string-value'" will return a Boolean and bind it to the variable. 
Whereas

<xsl:variable name="flag">
  <xsl:value-of select="$X = 'literal-string-value'" />
</xsl:variable>

will take the Boolean, turn it into a string, and put it into an RTF.

> Is there a way to take a 'results-tree-fragment' which has the value
> "true" or "false" and turn it back into the equivalent 'boolean' value?
Sure:

<xsl:variable name="flag" select="$rtf = 'true'"/> will bind $flag to 
Boolean true() only if the string value of $rtf is 'true'; otherwise it'll 
be false().

(true() and false() are functions that will return the Boolean true and 
false values respectively. They too may be useful to you.)

But any time you do <xsl:value-of select="$flag"/> you are coercing the 
Boolean back into a string, since that's what value-of does.

Cheers,
Wendell


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Wendell Piez                            mailto:wapiez@mulberrytech.com
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