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Why are constructor parameters made into members for case classes?


Why are constructor parameters made into members for case classes?

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Why are constructor parameters made into members for case classes?
Tag : scala , By : user147496
Date : November 26 2020, 01:01 AM


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Classes, constructor and pointer class members


Tag : cpp , By : iyogee
Date : March 29 2020, 07:55 AM
hope this fix your issue It depends on whether you want to share the underyling vector or not. In general, I think it is a good practice to avoid sharing wherever possible, since it removes the question of object ownership. Without sharing:
class ListHandler 
{
    public:
        ListHandler(const std::vector<int>& list) : _list(list) {}
        ~ListHandler(){}
    private:
        std::vector<int> _list;
};
class ListHandler 
{
    public:
        ListHandler(std::vector<int>& list) : _list(&list) {}
        ~ListHandler(){}
    private:
        std::vector<int>* _list;
};
class ListHandler 
{
    public:
        ListHandler(std::vector<int>* list) : _list(list) {}
        ListHandler(const ListHandler& o) : _list(new std::vector<int>(o._list)) {}
        ~ListHandler(){ delete _list; _list=0; }

        ListHandler& swap(ListHandler& o){ std::swap(_list,o._list); return *this; }
        ListHandler& operator=(const ListHandler& o){ ListHandler cpy(o); return swap(cpy); }
    private:
        std::vector<int>* _list;
};
class ListHandler 
{
    public:
        ListHandler(const boost::shared_ptr< std::vector<int> >& list) : _list(list) {}
        ~ListHandler(){}
    private:
        boost::shared_ptr< std::vector<int> > _list;
};

How to define case classes with members with unbound type parameters?


Tag : scala , By : Sharad
Date : March 29 2020, 07:55 AM
Does that help A type X[_] is hardly ever what you want. When you use _ on a type, you are basically saying you don't care what that parameter is, because you'll never need to use it.
Anyway, this compiles. It may well bite you down the road, existential types being the tricky stuff that they are, but...
case class University(p: Person[t] forSome { type t <: Person[t] })

Is it ok for case classes to have members of themselves?


Tag : scala , By : John Miller
Date : March 29 2020, 07:55 AM
Hope this helps This is a perfectly fine use of a case class. Case classes are great for defining Recursive structures like this.
For instance, if I wanted to define my own linked-list class, I could use a case class to facilitate easy pattern-matching functionality:
trait MyList[T]
case class Link[T](head: T, tail: MyList[T]) extends MyList[T]
case class End[T]() extends MyList[T]

@tailrec
def last[T](list: MyList[T]): Option[T] =
  list match {
    case End() => None
    case Link(head, End()) => Some(head)
    case Link(head, tail) => last(tail)
  }

println(last(Link(1, Link(2, Link(3, End())))))  // Some(3)
println(last(Link(1, End())))                    // Some(1)
println(last(End()))                             // None

Implicitly declared copy-constructor for classes without data-members and base-classes


Tag : cpp , By : Shitic
Date : March 29 2020, 07:55 AM
should help you out The implicitly declared copy constructor in both cases is of the form A(const A &), since that's the first case in the list and none of the restrictions apply.

How to add constructor without parameter, in case the base class having the constructor with parameters


Tag : java , By : Jouni
Date : March 29 2020, 07:55 AM
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