Something New Every Day

Playing in F# (61/365) Wednesday March 2, 2011

Been a very busy week, with the Bing launch in France, so I’ve had to grab my opportunities for new things when I can.

On Wednesday, I followed the advice of @phammond to try out some new programming languages when I’m stuck for ideas, and had a play with F#. F# is a functional programming language, which makes it very interesting to play about with as it forces you to think about problems in a slightly different way. After installing the software and figuring out how to get the console running, I managed to write some “Hello World” code:

module BraveLocation.FSharpDemo
open System
let output = “Hello World!”
System.Console.WriteLine output

The line that took a little time was when loading the above code from a file in the F# console, you need your code to be part of a module.

Pressing on, next step was to write a very simple function that takes 2 integers and adds them:

let sum2 a b = a + b
let testSum2Values = sum2 3 4
System.Console.Write “3+4=”
System.Console.WriteLine testSum2Values

All pretty straightforward, but the rather sparse syntax takes a little time to get used to.

Finally something a little more interesting, with a recursive function that adds all numbers in a list of integers:

let rec sumList c = match c with
                    | h::tail -> (sumList tail) + h   // A list has a value (h) and a tail
                    | [] -> 0                         // If the list is empty, return 0 to end the recursion
let testSumList = sumList [1;2;3;4;5]      // Define a list, and sum the values
System.Console.Write “1+2+3+4+5=”
System.Console.WriteLine testSumList

A few newbie things of note here:

• The “rec” in the function declaration denotes this function can be called recursively
• The built-in list type is really a linked list, with a value, and a ::tail denoting the list part
• The match clause is a sort of dynamic type matching switch statement

It’s all very interesting, and compiling to .Net makes it possible to easily mix and match languages as appropriate. Will definitely investigate more if I ever get time