Sunday, December 4, 2011

F# List

Last week Tuples group values into a single entity. List allows you link data together to form a chain. F# define a list as ; delimited values enclosed in brackets as:

let countDown = [9;8;7;6;5;4;3;2;1];;

F# has only two operations. They are (i) cons :: operator, to add an element in front of list (ii) append @ operator, to add at the last. Examples are:
>let countDown = 10::countDown;;

val countDown : int list = [10;9;8;7;6;5;4;3;2;1]

>let countDown = 0@countDown;;

val countDown : int list = [10;9;8;7;6;5;4;3;2;1;0]

List Range

To declare a list of ordered numeric values, List range specifies the lower and upper range as:
>let counter = [1..10];;

val counter : int list = [1;2;3;4;5;6;7;8;9;10]

List comprehension

Itz a rich syntax that allows you to generate list inline with F# code. The body of the list comprehension will execute until it terminates, and the list will be made up of elements returned via yield keyword.
let numbersNear x =
yield x-1
yield x
yield x+1
];; function creates a new collection by applying a function to the given collection. Just have a look on attached image example

When you print r1 the example, you should get the output as 2,3,4,5


It iterates thro each element of the list and calls a funtion that you pass as a parameter.

No comments:

Post a Comment