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Tip of the Day
Language: C++
Expertise: All
Mar 13, 1999



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

Prefer Initialization to Assignment of Objects

In general, assignment requires the creation and destruction of a temporary object, whereas initialization does not. This is true for not just for strings, but for every object type, so whenever you have the choice--prefer initialization to assignment. Consider this code snippet:
    string s1 = "Hello ",  s2 = "World", both;
    both = s1+s2;   // assignment rather than initialization; inefficient 
The compiler transforms the expression both = s1+s2; into:
    string temp (s1 + s2);  // store result in a temporary
    both = temp;   // assign 
    temp.Date::~Date();  // destroy temp
This snippet could have been written in a much more efficient way:
    string s1 = "Hello ",  s2 = "World";
    string both = s1+s2;  // initialization is more efficient than assignment
This time, the compiler transforms the expression both = s1+s2; into:
    string both (s1 + s2); 
Danny Kalev
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