Hi mobi phil,
One of the annoyances with std::map is that if you work with const maps, then there is no "one line" code to get an element knowing the key.
If that is really what you want and you don't care about performances, I can propose you for example the following : [code] #include <boost/foreach.hpp> #include <stdexcept> struct ConstMapHelper { template <class T,class U> static const U& getConst(const T& pKey,const std::map<T,U>& pMap) { typedef std::pair<const T,U> TPair; BOOST_FOREACH(const TPair& lPair,pMap) { if(lPair.first==pKey) { return lPair.second; } } throw std::domain_error("[ConstMapHelper::getConst] key not found"); // do what you want } }; [/code] And then when you want to use it : // construction of the const map std::map<std::string, std::string> lMap; lMap.insert(std::make_pair("1","1")); lMap.insert(std::make_pair("2","2")); const std::map<std::string, std::string> lMapConst(lMap); // access const std::string key = "5"; // the key const std::string& s = ConstMapHelper::getConst(key,lMapConst); // will throw exception because "5" is not in the map. You can even make it a true one liner if you get rid of the reference in the 'key' parameter. Hope this helps, Best regards, Pierre Morcello --- En date de : Mar 20.10.09, mobi phil <mobi@mobiphil.com> a écrit :
De: mobi phil <mobi@mobiphil.com> Objet: [boost] BOOST_FOREACH like macro for map À: boost@lists.boost.org Date: Mardi 20 Octobre 2009, 9h06 Hello,
new to this list... did not find anything similar on net.
One of the annoyances with std::map is that if you work with const maps, then there is no "one line" code to get an element knowing the key.
given the map
const map<string, string> aStringMap;
I cannot write
const string &s = aStringMap["key"]; process(s);
I should write:
map<string, string>::const_iterator it=aStringMap..find("key") if( it != aStringMap.end() ) { process(it->second) }
so would be nice to have a macro like
BOOST_CONSTMAPFIND(aStringMap, "key", data) { processResult( data ); }
the version
if(BOOST_CONSTMAPFIND(l_map, l_key, l_data) ) {
}
Seems to be impossible to implement
-- rgrds, mobi phil
being mobile, but including technology http://mobiphil.com _______________________________________________ Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost