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Tuple.md

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Tuple

A Tuple is a simple data type that represents two types of values at the same time. It is typically used to pass two values around without needing to introduce some adhoc data type, such as the accumulating state of an operation along with the previous result, or coupling an ID along with a set of values.

Note that while other libraries and languages may offer tuples of varying sizes, the Tuple currently offered here is restricted to holding two values.

Construction

Tuple consists of a single constructor that accepts the two values to store in the tuple Tuple :: a -> b -> Tuple a b. It is worth highlighting that the two values associated with the Tuple may be completely different types.

Interaction

The values of a Tuple instance can be accessed by passing the Tuple to Tuple.fst or Tuple.snd for the first and second values respectively.

Reference

Constructors

Tuple

:: (a, b) -> Tuple a b

Static functions

Tuple.fst

:: Tuple a b -> a

Returns the first element of a given Tuple.

Tuple.snd

:: Tuple a b -> b

Returns the second element of a given Tuple.

Instance methods

tuple.concat

:: (Semigroup a, Semigroup b) => Tuple a b ~> Tuple a b -> Tuple a b

Joins the Tuple instance with the given Tuple by concatenating the first elements of each Tuple to produce the first element of the returned Tuple and the second elements concatenated together to produce the returned second element. To ensure the elements can be concatenated together, both types of the Tuple elements must satisfy the Semigroup spec.

tuple.map

:: Tuple a b ~> (b -> c) -> Tuple a c

Transforms the second element of the Tuple instance by applying the given function over the value.

tuple.ap

:: Semigroup a => Tuple a (b -> c) ~> Tuple a b -> Tuple a c

Transforms the second element of the given Tuple by applying the function held in the second element of the Tuple instance. As this leaves both of the first elements unmodified, the two must be combined in some way to produce a single value to be stored in the first element of the returned Tuple. This is done by requiring that the type of value in the first element satsifies the Semigroup spec, with the resulting value determined by concatenating the two values together.

tuple.equals

:: Tuple a b ~> * -> Boolean

Determines whether the given Tuple is equal to the Tuple instance. This is determined by comparing the equality of values of the first element of each Tuple, then comparing the values of the second element of each.

tuple.toString

:: Tuple a b ~> () -> String

Returns a string representation of the Tuple instance.