[XSL-LIST Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Re: Question on translate() function
On Mon, 2017-09-25 at 17:42 +0000, Syd Bauman s.bauman@xxxxxxxxxxxxxxxx wrote: > > I have always presumed that translate() is faster than replace().[1] I'd say, use whichever is clearer, braver, more noble. Take pity on your future self trying to understand replace("[{]\\\$[()][}]", "#", "g")... As for which is faster, it depends not only (as the inestimable Dr Kay has expressed) upon the quality of the optimizer but for some implementations the quality of the underlying code. Unfortunately there are enough differences between XSLT and Perl regular expressions that using libpcre has become difficult, as that library gets extensive optimization outside of our universe and then returns through alternate dimensions to dazzle us :) > But I can't help it, sometimes -- I'd really like to know if > translate() is significantly more efficient (computationally) than > replace() or not. There's no inherent reason why translate("abc", "ddd") should be faster or slower than replace("[abc]", "d", "g") once the parsing has been done; however, the work to recognize these two cases may be easier for translate(). There are implementations that are faster than a freshly-oiled cow at recognizing regular expression character classes, so if your input string is, say, 100MBytes long, you might well be able to measure the difference. In ASCII days there were implementations that used a bit mask, and then you compare each input character (or four characters at a time, say, using a wider mask) with the or'd mask and only do the more expensive computation when needed. So an implementation using a heavily optimized regular expression library might go faster with replace() than translate(), because the XSLT/XPath/XQuery implementor of translate() might not have done that sort of optimization. Liam -- Liam Quin, W3C, http://www.w3.org/People/Quin/ Staff contact for Verifiable Claims WG, SVG WG, XQuery WG Web slave for http://www.fromoldbooks.org/
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