# Module Pair

    module Pair: sig .. end

Operations on pairs.

- Since 5.4

## Pairs

    type ('a, 'b) t = 'a * 'b

The type for pairs.

    val make : 'a -> 'b -> 'a * 'b

`make a b` is the pair `(a, b)`.

    val fst : 'a * 'b -> 'a

`fst (a, b)` is `a`.

    val snd : 'a * 'b -> 'b

`snd (a, b)` is `b`.

    val swap : 'a * 'b -> 'b * 'a

`swap (a, b)` is `(b, a)`.

## Iterators

    val fold : ('a -> 'b -> 'c) -> 'a * 'b -> 'c

`fold f (a, b)` applies `f` to `a` and `b`.

    val map : ('a -> 'c) -> ('b -> 'd) -> 'a * 'b -> 'c * 'd

`map f g (a, b)` applies `f` to `a` and `g` to `b`.

    val iter : ('a -> unit) -> ('b -> unit) -> 'a * 'b -> unit

`iter f g (a, b)` first applies `f` to `a`, and then `g` to `b`.

    val map_fst : ('a -> 'c) -> 'a * 'b -> 'c * 'b

`map_fst f p` applies `f` to `p`'s first component.

    val map_snd : ('b -> 'c) -> 'a * 'b -> 'a * 'c

`map_snd f p` applies `f` to `p`'s second component.

## Predicates and comparisons

    val equal : ('a -> 'a -> bool) -> ('b -> 'b -> bool) -> 'a * 'b -> 'a * 'b -> bool

`equal eqa eqb (a1, b1) (a2, b2)` is `true` if and only if `eqa a1 a2` and `eqb b1 b2` are both `true`.

    val compare : ('a -> 'a -> int) -> ('b -> 'b -> int) -> 'a * 'b -> 'a * 'b -> int

`compare cmpa cmpb` is a total order on pairs using `cmpa` to compare the first component, and `cmpb` to compare the second component. It is implemented by a lexicographic order.