问题
When initializing primitive types like int or pointers one can use either copy-initialization or direct-initialization.
int a = 10;
int b(10);
Although the latter way is preffered for objects with constructors, I don't see people using it for primitives. I understand that it is kind of "more natural" (especially for numbers) to use the '=' operator but is there anybody writing things like in real-life code:
for (int i(0); i < 5; ++i) {
cout << i << endl;
}
Thanks.
EDIT: The question asks about coding styles and best practices rather than technical implementation.
回答1:
Some people do this to be consistent.
Inside a template, the code could be
for (T i(0); i < 5; ++i) {
cout << i << endl;
}
and writing it that way everywhere would make the coding style consistent.
回答2:
Both are initialization using the copy constructor, even though the first looks like an assignment. It's just syntactic sugar.
You could check it easily with a class that prints out something at copy construction and something different at assignment.
And int being a primitive doesn't even come into play.
回答3:
I prefer the i = 0 style, it is easier to read, and you can also use it in like this:
if (int i = some_function())
{
}
Works also fine with pointers, and all other types convertible to bool:
if (const int* p = some_function())
{
}
if (shared_ptr<const int> q = some_function())
{
}
回答4:
I used to have a colleague doing so:
for (int i(0); i < 5; ++i) {
cout << i << endl;
}
and it really pissed everyone off. It's far easier to read the code using i = 0 than i(0). Maybe not in this example but, as a general rule, it is.
Even for complex objects, I always prefer the i = 0 style, it just feels more natural for the reader and any decent compiler will optimize the generated code so there is virtually no performance penalty.
来源：https://stackoverflow.com/questions/7091784/direct-initialization-vs-copy-initialization-for-primitives