[XSL-LIST Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] ($possibly-empty, $default)[1] idiom optimisation
Hi, This is often used as a nice way to avoid an if-then-else check to display $default if $possibly-empty is empty: ($possibly-empty, $default)[1] Out of interest, is it likely to be optimised to avoid evaluating $default if the first item is not empty, because if $default takes a reasonable amount of work to evaluate it's effectively wasted most of the time (if $default is rare). If it takes more work to evaluate $default than to test whether $possibly-empty is empty each time, then this is just a short cut rather than good practice. It reminds me of advice I heard (for Java) to wrap all log statements in an if test to check the log level first to avoid the unnecessary creation of the log message. For example, constructing a large message for a debug log by combining several different things, only for the constructed string to be discarded because the log level is info. (testing the log level a 1000 times is far better than creating and discarding 1000 strings) -- Andrew Welch http://andrewjwelch.com Kernow: http://kernowforsaxon.sf.net/
|
PURCHASE STYLUS STUDIO ONLINE TODAY!Purchasing Stylus Studio from our online shop is Easy, Secure and Value Priced! Download The World's Best XML IDE!Accelerate XML development with our award-winning XML IDE - Download a free trial today! Subscribe in XML format
|