I was reading a blog post by Chris Smith on F#. Firstly, a really good blog post and well worth a read if you are interested in learning the basics of F# as I am.
The first thing that struck me about F# and Chris’s blog was his explanation that in F# there typically wasn’t such a thing as a variable – because of the immutability of the “value” holders.
That doesn’t mean that we don’t get mutable value holders – they are available, but they need to be explicitly declared.
Have a look at the F# code below…
let x = "the original value"; printfn "x's value is '%s'" x;
If I were to try and change the value holder x, doing something like this…
x <- "the new one.";
I would get an error stating that the value was not mutable. To get a mutable value, I would need to declare it explicitly like this…
let mutable x = "the original value";
And then the value would be allowed to be changed.
After this simple explanation of a really basic principle of F#, I am beginning to get excited to learn what other differences there are in this language!