Recently I saw a quite old code in C++, where int var(12) was used instead of int var=12. Why does it work? And should I avoid writing this style of declaration?
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1 Answer
There are three ways of initializing variables are valid in C++.
type identifier = initial_value;
For example, to declare a variable of type int called x and initialize it to a value of zero from the same moment it is declared, we can write:
int a=5; // initial value: 5 type identifier (initial_value);
A second method, known as constructor initialization (introduced by the C++ language), encloses the initial value between parentheses (()):
int b(3); // initial value: 3 type identifier {initial_value};
Finally, a third method, known as uniform initialization, similar to the above, but using curly braces ({}) instead of parentheses (this was introduced by the revision of the C++ standard, in 2011):
int c{2}; // initial value: 2 You should check Documentation section Initialization of variables
2 Comments
Aluan Haddad
They are not equivalent.
() will perform certain narrowing conversions.Aluan Haddad
int a{1.0} is an error. int a(1.0) is legal. They are not the same.