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[standard-ml/en-en] infix functions

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David Pedersen 2013-12-05 12:43:13 +01:00
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@ -264,6 +264,24 @@ fun map f [] = []
(* map has type ('a -> 'b) -> 'a list -> 'b list and is called polymorphic. *)
(* 'a is called a type variable. *)
(* We can define functions as infix *)
fun plus (x, y) = x + y
infix plus
(* We can now call plus like "2 plus 5" *)
(* Functions can also be made infix before they are defined *)
infix minus
fun x minus y = x - y
(* An infix function/operator can be made prefix with "op" *)
val n = op + (5, 5)
(* n is now 10 *)
(* op is useful when combined with high order functions *)
val listSum = foldl op + 0 [1,2,3,4,5]
(* Datatypes are useful for creating both simple and complex structures *)
datatype color = Red | Green | Blue