c++iterate sequence, grouping every 4 items

https://github.com/tiger40490/repo1/blob/cpp1/cpp/binTree/serialize_deser.cpp has working solution that I came up myself

for(int i=0; getline(myStringstream,token, ','); ++i){
      v.push_back(token);
      if (i%4 < 3) continue;
      string id=v[0], idLe=v[2], idRi=v[3]; Data d=stoi(v[1]);
      v.clear();

 

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c++user-defined constant:(scoped)enum^const static

See https://stackoverflow.com/questions/112433/should-i-use-define-enum-or-const

  • best practice — enclose in a namespace or a class
  • enum can group 2 related constants. Scoped enum is even more descriptive.
  • enum also creates a typename for code documentation
  • enum const value must be signed integers 😦
  • Both enum type and a single static const field can be declared as class members 🙂
  • For singular constants, use enum or const static variables (file-scope, and independently instantiated in each compilation unit). Avoid extern.

private dtor restricts allocation to heap only

My test proves that merely declaring the a stack instance or global instance is illegal because compiler generates a (illegal) call to the private dtor!

Friend can also call dtor!

class PrivDtor{
  ~PrivDtor(){
        cout<<"dtor\n";
  }
public:
  static void destroy(PrivDtor* p){p->~PrivDtor();}
  static void del(PrivDtor* p){delete p;}
};

//PrivDtor globalInstance;  //won't compile
int main(){
  //PrivDtor stackInstance; //won't compile

  PrivDtor * p = new PrivDtor;
  //PrivDtor::del(p); // works!
  PrivDtor::destroy(p);  //works!
}

19obscure but recurr`c++QQ questions #halo

All QQ topics, not related to GTD or coding IV

  1. Throwing dtor
  2. how to avoid virtual functions (use enum?); CRTP
  3. IPC mutex; synchronization in shared mem
  4. Delete a pointer to base, but the actual object is a derived without virtual dtor. See my post https://bintanvictor.wordpress.com/2015/04/21/deleting-base-class-ptr-non-virt-dtor
  5. casting “this” pointer. See https://bintanvictor.wordpress.com/2017/11/15/crtp-1st-lesson/
  6. memory: placement new and how to delete
  7. reinterpret_cast
  8. why division by zero is not an exception
  9. debug build modifying behavior
  10. memory: q(delete this)
  11. SFINAE — I was asked in … 2 MS teams?

–socket programming interviews

  1. ##tcp tuning params
  2. non-blocking socket calls
  3. buffer full

#include <xtap/PluginConfig.h> trick

I have seen it in many large systems:

The actual path to the header is …/shared/tp_xtap/include/PluginConfig.h, but develoeprs prefer an abbreviated include like #include <xtap/PluginConfig.h>.

#1) Here’s one simple implementation:

ls -l shared/tp_xtap/include/ # should show a symbolic link to be created automatically:

    xtap -> ./

Therefore, -I/full/path/to/shared/tp_xtap/include/ will resolve #include <xtap/PluginConfig.h>

#2) I guess a second-best solution is code generation. Checked-in source file has #include <xtap/PluginConfig.h> but the build system follows configured rewrite-rules, to convert it into #include <some/other/path>