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My buddy and I have been recently reading leveldb source code. And we encounter this problem. In leveldb db/skiplist.h file, there is a constructor declaration:
explicit SkipList(Comparator cmp, Arena* arena);
I know explicit constructor with single parameter means no implicit type conversion for constructor parameter. But what does double parameters constructor with explicit keyword mean? Is it new rule of C++11?
Thanks.
956
The explicit function specifier controls unwanted implicit type conversions. It can only be used in declarations of constructors within a class declaration. For example, except for the default constructor, the constructors in the following class are conversion constructors.
implicit constructor is a term commonly used to talk about two different concepts in the language, the. implicitly declared constructor which is a default or copy constructor that will be declared for all user classes if no user defined constructor is provided (default) or no copy constructor is provided (copy).
With C++11, you can use braced-init-lists in place of some other expressions, and that makes a difference. For instance, you can use them in return statements:
SkipList foo() {
return {{}, nullptr}; //does not compile with explicit constructor
return SkipList{{}, nullptr}; //compiles with or without explicit constructor
}
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