Fn structure

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The Fn structure provides combinators for working with function values, including application, composition, currying, and fixpoint operators.

Synopsis

val id : 'a -> 'a
val const : 'a -> 'b -> 'a
val apply : ('a -> 'b) * 'a -> 'b
val o : ('b -> 'c) * ('a -> 'b) -> 'a -> 'c
val curry : ('a * 'b -> 'c) -> 'a -> 'b -> 'c
val uncurry : ('a -> 'b -> 'c) -> 'a * 'b -> 'c
val flip : ('a * 'b -> 'c) -> 'b * 'a -> 'c
val repeat : int -> ('a -> 'a) -> 'a -> 'a
val equal : 'a -> 'a -> bool
val notEqual : 'a -> 'a -> bool

id

id x returns the value x. (id is the polymorphic identity function.)

const

const x y returns the value x.

apply

apply (f, x) applies the function f to x. Thus, it is equivalent to f x.

o

f o g is the function composition of f and g. Thus, (f o g) a is equivalent to f (g a). This function is the same as the global o operator and is also part of the General structure.

curry

curry f x y is equivalent to f (x, y); i.e., curry f transforms the binary function f into curried form.

uncurry

ucurry f (x, y) is equivalent to f x y; i.e., uncurry f transforms the curried function f into a binary function. This function is the inverse of curry.

flip

flip f (x, y) is equivalent to f (y, x); i.e., flip f flips the argument order of the binary function f.

repeat

repeat n f returns the n-fold composition of f. If n is zero, then repeat n f returns the identity function. If n is negative, then it raises the exception Domain.

equal

equal a b returns whether a is equal to b. It is a curried version of the polymorphic equality function (=).

notEqual

notEqual a b returns whether a is not equal to b. It is a curried version of the polymorphic inequality function (<>).