Some basics of F#<\/p>\n
#light<\/strong><\/p>\n This directive (hash light) is used to simplify the F# syntax. Meaning the syntax is a little less verbose and removes aspects of the OCaml compatibility. <\/p>\n Immutable by default<\/strong><\/p>\n By default “variables” are really just “values” as they are immutable by default so <\/p>\n initializes n to the value 100 and you cannot now alter n. <\/p>\n However we can mark a value as mutable and thus is can be altered, for example<\/p>\n n is set to be a mutable type and n <- n + 1<\/em> is the assignment line of code, assigning n the new value of n + 1.<\/p>\n Assignment operator<\/strong><\/p>\n As mentioned above, F# values are immutable, by marking them as mutable we can assign values to them. The assignment operator is not = but is <-, for example\n\n[code language=\"fsharp\"]\nlet mutable n = 10 \/\/ initializes n the value 10\nn <- 100 \/\/ assignment of the value 100\n[\/code]\n\nignore<\/strong><\/p>\n Some functions return values which we might not actually wish to use. For example the following uses List.map to simply output the items in the array urls<\/p>\n But the compiler will show a warning This expression should have type ‘unit’, but has type ‘unit list’. Use ‘ignore’ to discard the result of the expression, or ‘let’ to bind the result to a name<\/em> for the line List.map f urls. To fix this either change this line to<\/p>\n or pipe the result to ignore as per<\/p>\n We can also use the following syntax<\/p>\n Semi-colon and commas in lists and arrays<\/strong><\/p>\n To declare a list value in F# we use a semi-colon to denote each value of a list for example<\/p>\n This will create a val evens : int list = [2; 4; 6; 8; 10; 12]<\/p>\n Alternatively using a comma as per<\/p>\n This will create a val evens : (int * int * int * int) list = [(2, 4, 6, 8)]. The difference here is that with the comma we’re creating a tuple containing integers, not a list of integers.<\/p>\n Collection Types<\/strong><\/p>\n List<\/em><\/p>\n A list is declared as <\/p>\n Lists are ordered, immutable data of the same type.<\/p>\n Array<\/em><\/p>\n An array is declared as<\/p>\n Array’s are fixed-size, zero based values of the same type.<\/p>\n Sequence<\/em><\/p>\n A sequence is declared as<\/p>\n A sequence is a series of values of the same type. <\/p>\n Lambda expressions and anonymous functions<\/strong><\/p>\n Anonymous functions are declared as follows<\/p>\n For example we might use an anonymous function in a List.map as follows<\/p>\n Comments<\/strong><\/p>\n Single line comments are denoted in the same way as C# i.e.<\/p>\n Multi-line comments are denoted using (*..*), i.e.<\/p>\n Loops<\/strong><\/p>\n The F# equivalent of a foreach<\/p>\n The for<\/em> loop<\/p>\n The while<\/em> loop<\/p>\n The unit type<\/strong><\/p>\n\r\nlet n = 100\r\n<\/pre>\n
\r\nlet mutable n = 100\r\nn <- n + 1\r\n<\/pre>\n
\r\nlet urls = ["http:\/\/www.bbc.co.uk";\r\n "http:\/\/www.google.co.uk";\r\n "http:\/\/www.amazon.co.uk"]\r\n\r\nlet f x = printfn "%s" x\r\nList.map f urls\r\n<\/pre>\n
\r\nlet o = List.map f urls\r\n<\/pre>\n
\r\nList.map f urls |> ignore\r\n<\/pre>\n
\r\nignore(List.map f urls)\r\n<\/pre>\n
\r\nlet evens = [2;4;6;8;10;12]\r\n<\/pre>\n
\r\nlet evens = [2,4,6,8,10,12]\r\n<\/pre>\n
\r\nlet list = [2;4;6;8;10]\r\n<\/pre>\n
\r\nlet array = [|2;4;6;8;10|]\r\n<\/pre>\n
\r\nlet s = seq { 0 .. 10 .. 100 }\r\n<\/pre>\n\r\nfun parameter-list -> expression\r\n<\/pre>\n
\r\nlet urls = ["http:\/\/www.bbc.co.uk";\r\n "http:\/\/www.google.co.uk";\r\n "http:\/\/www.amazon.co.uk"]\r\n\r\nList.map (fun x -> printfn "%s" x) urls\r\n<\/pre>\n
\r\n\/\/ This is a comment\r\n<\/pre>\n
\r\n(*\r\nThis is a comment block\r\n*)\r\n<\/pre>\n
\r\nlet a = [0 .. 6]\r\nfor i in a do\r\n printfn "%d" i\r\n<\/pre>\n
\r\nfor i = 1 to 10 do\r\n printfn "%d" i\r\n\r\nfor j = 10 downto 1 do\r\n printfn "%d" j\r\n<\/pre>\n
\r\nlet aa = [|0 .. 6|]\r\nlet mutable i = 0\r\n while i < (Array.length aa) do\r\n printfn "%d" (Array.get aa i)\r\n i <- i + 1\r\n<\/pre>\n