Re: [xsl] Do xsl processors contain optimizer for conditions?

[Martin Honnen <Martin.Honnen@xxxxxx>]

cert21 wrote:
> I know in many languages like Java and php when testing for multiple 
> conditions
> the engine is smart to return false when the first condition fails, so 
> it does not even check
> next conditions.
> This saves some of the processing time.
>
> I wonder if xsl engines follow the same logic, for example in test like 
> this:
>
> <xsl:when
>                test="( (string-length($mystring) > 30)  and 
> not(contains(substring($mystring, 1, 30), ' ') ) )">
>
> If the string-length is < 30 then the second condition will not even be 
> evaluated?

Technically it is a question about XPath expressions, if you look at the 
specification http://www.w3.org/TR/xpath#booleans then it clearly says 
for 'and' expressions:
  "The right operand is not evaluated if the left operand evaluates to 
false."

And for 'or' expressions:
  "The right operand is not evaluated if the left operand evaluates to 
true."

So it is not question about optimization, the language specification 
prescribes what to do.

--

	Martin Honnen
	http://msmvps.com/blogs/martin_honnen/