C++: "expected ;" in declaration in template -

-

i've been running following problem inside member function of templated class:

#include <map> using std::map; template <typename a,typename b> class c {   public:     b f(const a&,const b&) const;   private:     map<a,b> d; }; template <typename a,typename b> b c<a,b>::f(const a&a,const b&b) const {    map<a,b>::const_iterator x = d.find(a);    if(x == d.end())      return b;    else      return x->second; }

when have g++ compile following error:

bug.c: in member function 'b c<a,b>::f(const a&, const b&) const': bug.c:12: error:expected ';' before 'x' bug.c:13: error: 'x' not declared in scope

however, when make non-templated version of class , function, , b both being int compiles without problem. error little mystifying since can't imagine why wants ';' before 'x'.

you're missing typename:

typename map<a,b>::const_iterator x = d.find(a);

please read where , why have put “template” , “typename” keywords?. reason need typename here because a , b template parameters means meaning of ::const_iterator depends on a , b are. while human name const_iterator makes obvious iterator type, compiler doesn't know if type, data member, etc.

the compiler syntax check on first pass before templates instantiated , adding typename letting compiler know parse map<a,b>::const_iterator type.

also, there special rule in c++ (shamefully stolen linked question):

a name used in template declaration or definition , dependent on template-parameter assumed not name type unless applicable name lookup finds type name or name qualified keyword typename.

if not add typename, compiler has assume not type.


Comments

Post a Comment

Popular posts from this blog

mod rewrite - Using "?" when rewriting the URL -

-
i have been researching weeks looking how rewritting file/directory complementary "?" or "question mark" what need: http://mydomain.com/demo01.php to like: http://mydomain.com/?theme=jerus theme > simple directory need use websites products(in case themes) jerus > name of theme extra info: i plan on rewritting every url individually refrain wildcard varibles.** wouldn't easy instead of doing url rewriting put php in directory called theme , name index.php? http://mydomain.com/theme/?t=jerus but if you're re-writing urls make rule acutally make route this: http://mydomain.com/theme/jerus/ which waaaay prettier see question: using clean urls in restful api
Read more

.htaccess: Transfer name to index.php if not directory public -

-
i have piece of code: options followsymlinks <ifmodule mod_rewrite.c> rewriteengine on rewritecond %{request_filename} !-f rewritecond %{request_filename} !-d rewritecond %{request_filename} !-l rewriterule ^(.*)$ index.php?url=$1 [l] </ifmodule> <ifmodule !mod_rewrite.c> errordocument 404 /index.php </ifmodule> i don't know how allow directory name "public" inside folder .htaccess, other names dir should transfered index.php. how that? add rewritecond exclude public directory rewritecond %{request_filename} !-f rewritecond %{request_filename} !-d rewritecond %{request_filename} !-l rewritecond %{request_uri} ^/public(/.*)?$ rewriterule ^(.*)$ index.php?url=$1 [l] now, redirection work /public directories only. if want url have rest of path that's below public url=subfolder/page.php /public/subfolder/page.php use rewritecond %{request_filename} !-f rewritecond %{request_filename} !-d rewrit...
Read more

Admob integration with pygame in android -

-
hello curious know solution integrating admob app written in pygame subset android. have tried below things did' t work me :( still nothing working me may there no way :( try 1: followed google https://developers.google.com/mobile-ads-sdk/docs/admob/fundamentals#android solution has no code change build.xml modification didt works me :( try 2: tried below solutio also. http://www.michenux.net/android-admob-tutorial-461.html did't work me :( try 3: tried hack pythonactivity.java. getting below related errors. have googleadmobadssdk-6.4.1.jar in \pgs4a-0.9.4\libs path still below kind of error. below code: protected void oncreate(bundle savedinstancestate) { super.oncreate(savedinstancestate); //vrbilgi setcontentview(r_layout_main); // setcontentview(r.layout.main); // create adview // adview = new adview(this, adsize.banner, my_ad_unit_id); adview = new adview(this, adsize.banner,"a15...
Read more