Problem #2 came quite a bit faster. The yield syntax in F# is very similar to the C# iterator syntax and made translating this sample a breeze.

As a commenter posted, in problem #1, I would've been better served to use Seq.filter as opposed to Seq.choose for the purpose of filtering list. I've applied that here. One downfall of learning a new language is finding the right API. I spent a bit of time reading through the Seq documentation looking for the equivalent of the Where extension method and could only find chose. Lesson learned

// Find the sum of all the even-valued terms in the sequence which do not exceed four million.

let problem2() =

let rec fib prev cur = seq {

yield prev

if cur < 4000000 then

yield! fib cur (prev+cur)

}

fib 1 2

|> Seq.filter (fun x -> 0 = x % 2)

|> Seq.sum

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Hi,

I suggest this solution:

let problem2() =

Seq.unfold (fun (x, y) -> Some (x, (x + y, x))) (1, 0)

|> Seq.filter (fun x -> 0 = x % 2)

|> Seq.take_while ((>) 4000000)

|> Seq.sum

Today’s lesson: Seq.unfold. It’s not always easy to use, but it’s a very nice function. Here, it returns the infinite list of Fibonacci numbers.