| severaltipsaboutRegularExpressions 1.processfor"greedy" Bydefault,thequantifiersare"greedy",thatis,they matchasmuchaspossible(uptothemaximumnumberofper- mittedtimes),withoutcausingtherestofthepatternto fail.Theclassicexampleofwherethisgivesproblemsisin tryingtomatchcommentsinCprograms.Theseappearbetween thesequences/*and*/andwithinthesequence,individual *and/charactersmayappear.AnattempttomatchCcom- mentsbyapplyingthepattern /\*.*\*/ tothestring /*firstcommand*/notcomment/*secondcomment*/ fails,becauseitmatchestheentirestringduetothe greedinessofthe.*item. However,ifaquantifierisfollowedbyaquestionmark, thenitceasestobegreedy,andinsteadmatchestheminimum numberoftimespossible,sothepattern /\*.*?\*/ |
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2004-02-14 09:33
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