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Tip of the Day
Home » Tip Bank » C++
Language: C++
Expertise: Intermediate
Oct 7, 1999



Building the Right Environment to Support AI, Machine Learning and Deep Learning

The Uses of Fundamental Types' Constructors

You can initialize variables of fundamental types by invoking their constructor:
  int n = int();  /* zero initialized */ 
  char c = char();  /* ditto */ 
  short *ps = new short(0);  /* ps points at a zero-initialized short */ 
Apparently, the constructor-like syntax seems redundant; after all, you can use the traditional initialization syntax:
  int n = 0;   
  char c = 0;
So is it just an interesting bit of trivia? No, it isn't. The constructor-initialization form is the only way to initialize dynamically allocated variables. Consider
  short *ps = new short(0);
Without the constructor initialization, ps would point to a short with an indeterminate value. More importantly, generic algorithms and containers rely on this form to provide a uniform interface for fundamental types and user-defined types alike. Thus, a vector <int> can copy-construct its elements in exactly the same way as a vector<string> does.
Danny Kalev
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