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Polymorphic Return Types in MATLAB


Polymorphic Return Types in MATLAB

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Polymorphic Return Types in MATLAB
Tag : matlab , By : Arnaud Goudsmit
Date : December 01 2020, 05:00 PM

hop of those help? You can't actually specify the return type in Matlab, you just return a value. The same function can easily return different types under different conditions. You can verify that there is no type information in function definitions by looking at the documentation.
For example, look at this function, which can return a string or matrix, based on the input argument:
function r = strange(arg)
   if arg == 1
       r = 'string';
   else
       r = [1, 2; 3 4];
   end
end
function r = evenstranger()
    if rand < 0.5
        r = 'string';
    else
        r = [1, 2; 3, 4];
    end
end

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C++ polymorphic functions with differing return types


Tag : cpp , By : new Blackberry devel
Date : March 29 2020, 07:55 AM
this one helps. I am creating a property class which stores a unique key and an arbitrary value as strings (plus an optional comment string for use when writing to configuration files). Currently I'm using the method of creating a base property class which holds the raw strings, and then subclassing this into type-specific properties - eg. an IntProperty which implements a getValue() function that converts the string to an int - to avoid having to convert a property value manually from a string every time I want to read it. These subclasses use getPropertyType(), a virtual function defined in the base and overridden in each of the derived, to return an enum value to identify which type of property they hold, and the base class returns a "none" identifier. , What about this? (Untested, but you should get the idea)
class BaseType {
public:
    virtual void getValue(string &s) { s = "";                            };
    virtual void getValue(int &i)    { i = 0;                             };
    virtual void getValue(double &d) { d = 0.0;                           };
};

class IntType : public BaseType {
public:
    virtual void getValue(string &s) { s = to_string(myvalue);            };
    virtual void getValue(int &i)    { i = myvalue;                       };
    virtual void getValue(double &d) { d = static_cast<double>(myvalue);  };
private:
    int myvalue;
};

class DblType : public BaseType {
public:
    virtual void getValue(string &s) { s = to_string(myvalue);            };
    virtual void getValue(int &i)    { i = static_cast<int>myvalue;       };
    virtual void getValue(double &d) { d = myvalue;                       };
private:
    double myvalue;
};

class StrType : public BaseType {
public:
    virtual void getValue(string &s) { s = myvalue;                       };
    virtual void getValue(int &i)    { i = stoi(myvalue);                 };
    virtual void getValue(double &d) { d = stod(myvalue);                 };
private:
    string myvalue;
};

Polymorphic return types in C++


Tag : cpp , By : user103892
Date : March 29 2020, 07:55 AM
hop of those help? So you have types Inf1 and Inf2, which are related to each other, and at least one of them contains abstract methods.
You want to return some sub-implementation of Inf2, but which one is decided at run time.

F-Bounded Polymorphic return types in Scala?


Tag : scala , By : LucaN
Date : March 29 2020, 07:55 AM
Does that help As @Rado Buransky pointed out, you cannot just omit the type constructor parameter by using an underscore. The following works for example:
def testBounds[T <: Upper[T]](make: => T): Unit = {
  val upper: T = make
  val mapped = upper.map()
  mapped.map().map().map()
}

testBounds(new Impl)
def testBounds: Unit = {
  val upper: Upper[T] forSome { type T <: Upper[T] } = new Impl
  val mapped = upper.map()
  mapped.map().map().map()
}

Why is it not possible use primitive types with polymorphic return types?


Tag : java , By : Frank Rotolo
Date : March 29 2020, 07:55 AM
help you fix your problem As always with these questions, the answer is that you'd have to ask the language designers. I can't see any reason why this couldn't be done. However in my opinion this feature would be fairly pointless. As you point out in the question it's only when moo is invoked on a variable of static type IntFoo that a primitive would get returned; on a variable of type Foo, an Integer would get returned anyway. So you can achieve essentially the same thing by doing this.
public class IntFoo implements Foo<Integer> {

    @Override
    public Integer moo() { return mooAsInt(); }

    public int mooAsInt() { return 0; }
}

Haskell: How can I set polymorphic types of arguments and return types


Tag : haskell , By : ERaubenheimer
Date : March 29 2020, 07:55 AM
may help you . Change the type of poly? Right now nothing keeps you (or some random library) from adding e.g. a Poly Double Int instance, which is why the type of 3 in poly 3 is ambiguous.
You could do
instance Poly a where
    poly :: a -> a
instance Poly a b | b -> a where
    poly :: a -> b
class Poly b where
    type Arg b :: *
    poly :: Arg b -> b

instance Poly Int where
    type Arg Int = Int
    poly x = x
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