Project Euler is a awesome site.   When working with a new language it can be tricky to find problems that need solving, that are more complex than "Hello World" and simpler than a full blown application. Project Euler gives use just that, cool and thought provoking problems that usually don't take days to solve. 

I've solved a number of questions with C# and some with Java.  BTW, I used Java because it had BigInteger support before .Net.

A couple weeks ago, back when winter had a firm grip on Columbus, OH, I began playing (researching) with F#.  I began with Problem #1 from Project Euler.  I started by looking at my solution in C#.

Here is my solution in C#.

   1:  using System;

   2:  using System.Collections.Generic;

   3:   

   4:  namespace Problem001

   5:  {

   6:      class Program

   7:      {

   8:          static void Main(string[] args)

   9:          {

  10:              List<int> values = new List<int>();

  11:   

  12:              for (int i = 1; i < 1000; i++)

  13:              {

  14:                  if (i % 3 == 0 || i % 5 == 0)

  15:                      values.Add(i);

  16:              }

  17:              int total = 0;

  18:   

  19:              values.ForEach(v => total += v);

  20:   

  21:              Console.WriteLine(total);

  22:              Console.ReadKey();

  23:          }

  24:      }

  25:  }

Now, after much tweaking and learning, here is my solution in F#.

   1:  open System

   2:   

   3:  let calc n = 

   4:      [1..n]

   5:      |> List.map (fun x -> if (x % 3 = 0 || x % 5 = 0) then x else 0)

   6:      |> List.sum

   7:   

   8:  let main() = 

   9:      calc 999

  10:      |> printfn "result = %d"

  11:      Console.ReadKey(true) |> ignore 

  12:   

  13:  main()

Just this little example highlights some cool things about F#.

• Type inference. F# infers the type of a value.  In the C# code above we declare a number of variables, the list, and a couple ints.  F# does not require this, it infers the calc (a function) accepts a int and returns a int.
• Great built in functionality for Lists.  List.map for example.

BTW, I don’t think I’m spilling the beans by giving away the code for Problem 1.  It by far is the easiest question, IMHO, solved by 92,000+ people.

Next I’ll look into writing a class library with F#.