Re: [xsl] XPath 3.0 is a composable language ... what does that mean?

[Michael Kay <mike@xxxxxxxxxxxx>]

On 24/10/2012 12:06, Costello, Roger L. wrote:
> Hi Folks,
>
> I read this in the XPath 3.0 specification:
>
>      XPath 3.0 is a composable language
>
> What does that mean?

It means that every operator / language construct allows any expression 
to appear as its operand, subject only to operator precedence and data 
typing constraints. For example, you can do

3 + max(for $i in 1 to 10 return (if ($i gt 5) then $i*3 else $i*2)))

Contrast this with XSLT, which is not fully composable: XPath 
expressions can be used as operands to XSLT instructions, but not the 
other way around; similarly Java has constructs called statements that 
cannot be nested inside expressions.

Michael Kay
Saxonica