Learn FSHARP with Real Code Examples

let mutable count = 0
let mutable isDark = false

let updateUI() =
    printfn "Counter: %d" count
    printfn "Theme: %s" (if isDark then "Dark" else "Light")

let increment() = count <- count + 1; updateUI()
let decrement() = count <- count - 1; updateUI()
let reset() = count <- 0; updateUI()
let toggleTheme() = isDark <- not isDark; updateUI()

// Simulate actions
updateUI()
increment()
increment()
toggleTheme()
decrement()
reset()

Demonstrates a simple counter with theme toggling using F# variables and console output.

let add a b = a + b
let subtract a b = a - b
let multiply a b = a * b
let divide a b = a / b

printfn "Add 5 + 3: %d" (add 5 3)
printfn "Subtract 5 - 3: %d" (subtract 5 3)
printfn "Multiply 5 * 3: %d" (multiply 5 3)
printfn "Divide 6 / 2: %d" (divide 6 2)

Demonstrates basic arithmetic operations using functions.

let rec factorial n =
    if n <= 1 then 1
    else n * factorial (n - 1)

printfn "Factorial of 5: %d" (factorial 5)

Recursive factorial function in F#.

let rec fibonacci n =
    if n = 0 then 0
    elif n = 1 then 1
    else fibonacci(n-1) + fibonacci(n-2)

[0..9] |> List.iter (fun n -> printfn "%d" (fibonacci n))

Recursive Fibonacci sequence generator.

let numbers = [1..10]
let squares = [for n in numbers do if n % 2 = 0 then yield n * n]
printfn "%A" squares

Using list comprehension to square even numbers.

let scores = dict ["Alice",10; "Bob",5; "Charlie",12]
let highScores = scores |> Seq.filter (fun kv -> kv.Value >= 10) |> dict
printfn "%A" highScores

Filtering a map based on values.

let add = fun x y -> x + y
printfn "%d" (add 3 7)

Using anonymous functions and piping.

let numbers = [1;2;3;4;5]
let sum = List.fold (fun acc x -> acc + x) 0 numbers
printfn "%d" sum

Summing a list of numbers using List.fold.

let xs = [1;2;3]
let ys = [4;5;6]
let sums = List.map2 (+) xs ys
printfn "%A" sums

Combining two lists using zip and map.

let addPair (x,y) = x + y
printfn "%d" (addPair (3,7))

Using pattern matching to destructure tuples.