c++ - How to return a vector reference from a function? -

-

i trying return vector function. if return whole vector, copying process take time, trying return reference vector only. how do in c++ ? here's current function,

vector<ii>& primefactors(int n)     {         int i;         vector<ii> factors;         for(i=0; i<=n && n!=1 ; ++i)         {             int cnt = 0;             while((n%primes[i]) == 0)             {                 ++cnt;                 n/=primes[i];             }             if(cnt!=0)                 factors.push_back({primes[i],cnt});         }         if(i == lim)             factors.push_back({n,1});            return factors;     }

and heres calling in main()

vector<ii> factors = primes.primefactors(20);

but if return whole vector, copying process take time, trying return reference vector only.

don't worry that. compiler optimize call via rvo (return value optimization) , elide copies. return vector value:

std::vector<ii> primefactors(int n) { … }

Comments

Post a Comment

Popular posts from this blog

windows - Single EXE to Install Python Standalone Executable for Easy Distribution -

-
i used pyinstaller create standalone exe file pyqt project. did not use single file option because exe created single file option takes long open. therefore, pyinstaller created dist folder contains bunch of files including program.exe file. create setup.exe file place contents of dist folder in program directory , create shortcut in start menu , on desktop. want super simple user. maybe setup.exe files when download program cnet. found inno-setup, looks promising. however, not know if there special considerations because program standalone program create python/pyqt program. thanks! have experience task? there program using task not know about? inno-setup or nsis easiest use. tell them files include , put them , create nice installer you. wrote short tutorial on experiences using innosetup might find helpful: http://www.blog.pythonlibrary.org/2008/08/27/packaging-wxpymail-for-distribution/ note tutorial based around wxpython app wrote, concepts same.
Read more

c# - Access objects in UserControl from MainWindow in WPF -

-
i have simple xaml, how can change text property of textblock in usercontrol1 mainwindow ? <window x:class="refactorxaml.mainwindow" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:refactorxaml="clr-namespace:refactorxaml" title="mainwindow" height="350" width="525"> <grid> <grid.rowdefinitions> <rowdefinition height="100"></rowdefinition> <rowdefinition height="100"></rowdefinition> </grid.rowdefinitions> <grid> <refactorxaml:usercontrol1></refactorxaml:usercontrol1> </grid> <grid grid.row="1"> <button>change text</button> </grid> </grid> </window> <usercon...
Read more

javascript - How to name a jQuery function to make a browser's back button work? -

-
i'm trying write function ajaxyfy web site, works perfect, except function button. that's have now: function loading() { if (typeof history.pushstate !== "undefined") { var historycount = 0; $('.menu-item, .logo').on('click','a',function(e){ e.preventdefault(); $(this).data('clicked', true); if ($(this).is('.logo a')) { var homepage = $(this).attr('href'); function1(homepage); history.pushstate(null, null, homepage); } else if ($(this).is('.projects a')) { var projects = $(this).attr('href'); function2(projects); history.pushstate(null, null, projects); } else { var pages = $(this).attr('href'); function3(pages); history.pushstate(null, null, pages); ...
Read more