Arrays

Lists are the central datatype in applicative programming. In imperative programming the array is the central datatype. Arrays are provided in a type-safe way in Standard ML through the use of the following operations of the Array structure in the Standard ML library.

• the type 'a Array.array;
• the creation functions Array.array of type (int * 'a) -> 'a Array.array and
  Array.fromList of type 'a list -> 'a Array.array;
• the Array.update operation of type ('a Array.array * int * 'a) -> unit; and
• the operation Array.sub with type ('a Array.array * int) -> 'a with exception Subscript. Subscripting begins from 0.

The Array.array type constructor admits equality and the equality which is provided is equality of reference. Thus, given the following declarations,

val a = Array.fromList [1];
val b = Array.fromList [1];

then a and b are not equal.

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