![\"cplusplus.jpg\"](\"http:\/\/bobbeaty.com\/wp\/wp-content\/uploads\/2007\/10\/cplusplus.jpg\")
<\/p>\n<\/p>\n
Today I got a somewhat sketchy bug report that, if it was true, would possibly<\/em> have pointed to a section in my code where I was deleting things from an STL std::map using the erase()<\/tt> method whose argument was an iterator on the std::map. The original code looked something like this:<\/p>\n where my thinking was that the iterator would be updated to the next, valid element after the erase. I think that was a major<\/em><\/strong> boo-boo. In all honesty, I didn't really know, but it seemed<\/em> to test OK, and so it went. The problem is that after the call to erase()<\/tt> the iterator, ia<\/tt>, is invalid and can't be moved to the next valid element in the iteration.<\/p>\n I did a little searching on this as I was sure<\/strong> there was something simple about this. What I read was that the right way to do this was to take advantage of the properties of the post-increment operator which will increment the value (move it to the next element) but return the original<\/em> value. So the code becomes:<\/p>\n In this code, the iterator is moved to the next valid element and yet the original iterator value is returned to the argument of erase()<\/tt>. This then removes the element from the map and we're sitting on the next, good one.<\/p>\n I like this a lot more, and it's clear what I should<\/em> have done all along. I won't forget this guy.<\/p>\n","protected":false},"excerpt":{"rendered":" Today I got a somewhat sketchy bug report that, if it was true, would possibly have pointed to a section in my code where I was deleting things from an STL std::map using the erase() method whose argument was an iterator on the std::map. The original code looked something like this: InstrumentAliasMap::iterator ia = mInstruments.begin(); […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[3,6],"tags":[],"class_list":["post-729","post","type-post","status-publish","format-standard","hentry","category-coding","category-cube-life"],"_links":{"self":[{"href":"https:\/\/bobbeaty.com\/wp\/wp-json\/wp\/v2\/posts\/729","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/bobbeaty.com\/wp\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/bobbeaty.com\/wp\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/bobbeaty.com\/wp\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/bobbeaty.com\/wp\/wp-json\/wp\/v2\/comments?post=729"}],"version-history":[{"count":0,"href":"https:\/\/bobbeaty.com\/wp\/wp-json\/wp\/v2\/posts\/729\/revisions"}],"wp:attachment":[{"href":"https:\/\/bobbeaty.com\/wp\/wp-json\/wp\/v2\/media?parent=729"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/bobbeaty.com\/wp\/wp-json\/wp\/v2\/categories?post=729"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/bobbeaty.com\/wp\/wp-json\/wp\/v2\/tags?post=729"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}} InstrumentAliasMap::<\/span>iterator<\/span> ia =<\/span> mInstruments.begin<\/span>(<\/span>)<\/span>;<\/span>\n while<\/span> (<\/span>ia !=<\/span> mInstruments.end<\/span>(<\/span>)<\/span>)<\/span> {<\/span>\n if<\/span> (<\/span>ia-><\/span>first ==<\/span> anInstrument)<\/span> {<\/span>\n \/\/ found a match - erase it<\/span>\n mInstruments.erase<\/span>(<\/span>ia)<\/span>;<\/span>\n }<\/span> else<\/span> {<\/span>\n \/\/ no match, check the next one<\/span>\n ++<\/span>ia;<\/span>\n }<\/span>\n }<\/span><\/pre>\n InstrumentAliasMap::<\/span>iterator<\/span> ia =<\/span> mInstruments.begin<\/span>(<\/span>)<\/span>;<\/span>\n while<\/span> (<\/span>ia !=<\/span> mInstruments.end<\/span>(<\/span>)<\/span>)<\/span> {<\/span>\n if<\/span> (<\/span>ia-><\/span>first ==<\/span> anInstrument)<\/span> {<\/span>\n \/\/ found a match - erase it<\/span>\n mInstruments.erase<\/span>(<\/span>ia++<\/span>)<\/span>;<\/span>\n }<\/span> else<\/span> {<\/span>\n \/\/ no match, check the next one<\/span>\n ++<\/span>ia;<\/span>\n }<\/span>\n }<\/span><\/pre>\n