Raina Dong's List: Job Hunting - Programming languages

• A copy constructor is generally needed when an object owns pointers or non-shareable references such as to a file and then you usually need a destructor and an assignment operator, too

• How will you declare an abstract base class
• explicit constructor
• conversion constructor
• protected constructor
• provide a public static method
• How can you write a class that ensures that its instance will be created on the heap

• protected:

      HeapOnly
• static HeapOnly * create() { return new HeapOnly; }
• destructor virtual

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• a local variable is declared static
• variable retains the value between function calls
• if a global variable is declared static, it can only be accessed in that file
• scope limitations

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• multiple Inheritance

• What does extern mean in a function declaration?
• extern is more useful when you are compiling a shared library
• makes the described variable or function usable by the succeeding part of the current source file
• If a declaration for an identifier already exists at file scope, any extern declaration of the same identifier found within a block refers to that same object. If no other declaration for the identifier exists at file scope, the identifier has external linkage.

• a[] = “string”;
   char *p = “string”;

   

  The difference is this:
    p is pointing to a constant string, you can never safely say
    p[3]=’x';
    however you can always say a[3]=’x';

   

  char a[]=”string”; - character array initialization.
    char *p=”string” ; - non-const pointer to a const-string.( this is permitted only in the case of char pointer in C++ to preserve backward compatibility with C.)
• Global to the file only (this is only a scoping issue.. it is still technically a global variable, but is hidden from all other source files by the compiler), make the variable static.

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• allow functions and classes to operate with generic types
• especially when combined with multiple inheritance and operator overloading
• template <typename T>
• T& maximum(const T& x,const T& y)
• The programmer may decide to implement a special version of a function (or class) for a certain type which is called template specialization
• template <>
• maximum<complex>
• Class templates are often used to define the methods and sub-types of generic containers.
• class template
• Both macros and templates are expanded at compile-time. Macros are always expanded inline, whereas templates are only expanded inline when the compiler deems it appropriate.
• template functions will have run-time overhead when they are not expanded inline
• Since the compiler generates additional code for each template type, indiscriminate use of templates can lead to code bloat, resulting in larger executables

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• if someone will derive from your class
• and if someone will say
• new Derived, where Derived is derived from your clas
• and if someone will say delete p, where the actual object's type is Derived but the pointer p's type is your class
• make your destructor virtual if your class has any virtual functions
• simplified rule of thumb

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• • You do a delete p.  
  • It is possible that p actually points to a derived class.
• • You do a delete p.  
  • It is possible that p actually points to a derived class.
• • You do a delete p.  
  • It is possible that p actually points to a derived class.
• • You do a delete p.  
  • It is possible that p actually points to a derived class.
• delete
• • You do a delete p.  
  • It is possible that p actually points to a derived class.
• • You do a delete p.  
  • It is possible that p actually points to a derived class.

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