Are tuples covariant?

Are tuples covariant?

In Python, most immutable containers are covariant. Tuples and frozensets (their type is FrozenSet ) are the most significant ones. But there are other covariant types as well.

Is IEnumerable covariant?

Several generic interfaces have covariant type parameters, for example, IEnumerable, IEnumerator, IQueryable, and IGrouping. All the type parameters of these interfaces are covariant, so the type parameters are used only for the return types of the members.

What is list tuple in C#?

Also you can store different data types in a list in contrast to an array where all data should have the same data type. If you want replace multi-dimensional arrays you can use List Tuples like. // var listCountryPopulation = new List>(); listCountryPopulation.

How do you calculate covariance in Python?

The covariance may be computed using the Numpy function np. cov() . For example, we have two sets of data x and y , np. cov(x, y) returns a 2D array where entries [0,1] and [1,0] are the covariances.

What does covariant mean?

: varying with something else so as to preserve certain mathematical interrelations.

Is covariant a list?

This is because lists are immutable and arrays are mutable. The difference is that List s are immutable while Array s are mutable. To understand why mutability determines variance, consider making a mutable version of List – let’s call it MutableList .

What is tuple with example?

Tuple is a collection of values separated by comma and enclosed in parenthesis. Unlike lists, tuples are immutable. The immutability can be considered as the identifying feature of tuples. I will explain the features of tuples and operations on them with examples.

When would you use a tuple?

Tuples are more memory efficient than the lists. When it comes to the time efficiency, again tuples have a slight advantage over the lists especially when lookup to a value is considered. If you have data which is not meant to be changed in the first place, you should choose tuple data type over lists.

How do you call a tuple in C#?

You can instantiate a Tuple object by calling either the Tuple constructor or the static Tuple. Create(T1, T2) method. You can retrieve the values of the tuple’s components by using the read-only Item1 and Item2 instance properties.

How covariance is calculated?

Covariance is calculated by analyzing at-return surprises (standard deviations from the expected return) or by multiplying the correlation between the two variables by the standard deviation of each variable.

What is the difference between correlation and covariance?

Put simply, both covariance and correlation measure the relationship and the dependency between two variables. Covariance indicates the direction of the linear relationship between variables while correlation measures both the strength and direction of the linear relationship between two variables.

What is the formal definition of covariance in typing?

The formal definition of the covariance is as follows (I slightly modified the definition from mypy docs ): for SubType <: SuperType. A generic type is, basically, a type that takes other types as its parameters, in square brackets, like Tuple, List, Union (see mypy docs ). In my first blog post about typing, I called it a “complex type”.

How is the covariance of a union type?

Union type is covariant in all its arguments: for SubType1 <: SuperType1, SubType2 <: SuperType2 (etc.). The covariance of Union basically works the same way as the covariance of Tuple. Let’s say we have two pairs of types: Dog <: Animal and Meat <: Food.

Which is covariant in the return type of callable?

So Callable is covariant in the return type. In more general terms, anything that provides something — producer, factory, constructor, writer, etc. — is covariant in the type of the objects it provides. It needs to be read-only with regard to the provided objects, though.

Which is the contrary term to covariance?

Contrary term to “covariance” is “contravariance”. It’s defined as follows: for SubType <: SuperType. The definition is almost the same as of “covariance”, but with <: relation switched.