## Wednesday, May 14, 2008

### missing ( before formal parameters

## Thursday, February 28, 2008

### Some Fun Generating 'the power of' With F#

So for my first bit of fun with F# I figured it'd be fun to play with the BigNum (used for crazy big numbers) I figured I write up some quick functions that simple generate the power of some number, resulting in some crazy big numbers :)

(*all of my examples include '#light')

My first function doesn't use the BigNum but it's very simplistic.

let rec pwrof x y =

if y = 1 then

x

else

x * pwrof x (y - 1)

So for everyone new to F# 'pwrof' is a recursive function that takes 2 ints. 'rec' lets the compiler know that the function is recursive and the 2 parameters get resolved down to being ints at compile time. This came pretty naturally for me coming from a C# world, so lets try to mix it up a bit.

let rec pwrof x y =

match y with

| 1 -> x

| _ -> x * pwrof x (y - 1)

This function does the exact same thing, but instead of using a familiar if/else statement we're using pattern matching (these are widely used in F#). It's like a switch statement. If y matches 1 then we return x, otherwise if y matches anything else, '_', then we recurse.

These were kinda fun, but I wanted to calculate crazy big power of calculations like 5000^5000. So here's an example that resembles my first function

let bpwrof x y =

let x = Microsoft.FSharp.Math.BigNum.of_int x

let pwr = x

let rec pwrof x y =

if y = 1 then

x

else

pwrof (x * pwr) (y - 1)

pwrof x y

And here's an example that resembles my second function

let bpwrof x y =

let x = Microsoft.FSharp.Math.BigNum.of_int x

let pwr = x

let rec pwrof x y =

match y with

| 1 -> x

| _ -> pwrof (x * pwr) (y - 1)

pwrof x y

These are tail recursive so you can create some really, REALLY big numbers. If you call one of the last 2 functions you can calculate say 5000 to the 9000th power. It ends up taking a lot more time to print the result to the screen than it does to do the calculation(its pages and pages of number madness). I even tried 5000 to the 90,000th pwr, that's a big number.

Oh well, that's all for now...

## Sunday, February 17, 2008

### F# again

I'm not one that enjoys scouring the web for information on things so I usually just go buy a book on whatever it is that I'm interested in. I decided the other day to head down to the local Borders and there was one copy left of Robert Pickering's F# book, titled 'Foundations of F#'. I'm currently only a few chapters in but it seems like a pretty good book thus far. It hasn't required a background in functional programming which is good and also seems to be a good read for the novice to expert programmers.

Well that's all for now, maybe next time I'll have some F# knowledge to share :)