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| -rw-r--r-- | fsharp.html.markdown | 7 |
1 files changed, 6 insertions, 1 deletions
diff --git a/fsharp.html.markdown b/fsharp.html.markdown index e345201d..69f4eb60 100644 --- a/fsharp.html.markdown +++ b/fsharp.html.markdown @@ -175,7 +175,12 @@ module ListExamples = // list comprehensions (aka generators) let squares = [for i in 1..10 do yield i * i] - // prime number generator + // A prime number generator + // - this is using a short notation for the pattern matching syntax + // - (p::xs) is 'first :: tail' of the list, could also be written as p :: xs + // this means this matches 'p' (the first item in the list), and xs is the rest of the list + // this is called the 'cons pattern' + // - uses 'rec' keyword, which is necessary when using recursion let rec sieve = function | (p::xs) -> p :: sieve [ for x in xs do if x % p > 0 then yield x ] | [] -> [] |