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The Haskell const function
The const function is simple, but you can use it to make your code more legible. In this example we convert a unary function to a function of arity 2 (that ignores the second argument). Also by using the flip function from Haskell (which is equally easy to define) you can ignore the first argument.
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// The const function
let ct a _ = a
// The flip function; even though I'm not gonna use it here
let flip f x y = f y x
// And now a use case
// I'm writing a toy interpreter so the following code is taken straight
// from that
type Exp =
// ...
// Lambdas are expressed as F# an function that takes a list of Exps and an env
 Lambda of (Exp list > Env > Exp)
// ...
and Env = (string * Exp) list
// Builtins receive evaluated arguments so they don't care about the env.
// By composing the function we get with ct we're basically converting a function
// of arity 1 to a function of arity 2 that just ignores its second argument
let builtin f = Lambda (f >> ct)

val ct : a:'a > 'b > 'a
Full name: Script.ct
val a : 'a
val flip : f:('a > 'b > 'c) > x:'b > y:'a > 'c
Full name: Script.flip
val f : ('a > 'b > 'c)
val x : 'b
val y : 'a
type Exp =  Lambda of (Exp list > Env > Exp)
Full name: Script.Exp
union case Exp.Lambda: (Exp list > Env > Exp) > Exp
type 'T list = List<'T>
Full name: Microsoft.FSharp.Collections.list<_>
type Env = (string * Exp) list
Full name: Script.Env
Multiple items
val string : value:'T > string
Full name: Microsoft.FSharp.Core.Operators.string

type string = System.String
Full name: Microsoft.FSharp.Core.string
val builtin : f:(Exp list > Exp) > Exp
Full name: Script.builtin
val f : (Exp list > Exp)
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