Immutable values in F#

Question

I'm just getting started in F# and have a basic question.

Here's the code:

let rec forLoop body times =
    if times <= 0 then
        ()
    else
        body()
        forLoop body (times - 1)

I don't get the concept of how when you define a variable it is a value and immutable. Here, the value is changing in order to loop. How is that different from a variable in C#?

Answer 1

it is not changing. you use recursion. that variable remains unchanged, but it is subtracted one and passed to function. function is same in this case.

stack will look like

forLoop body 0
 |
 forLoop body 1
   |
   forLoop body 2