How to pass string variables as arguments in function in OCaml?

Question

I wrote a simple code for a function which takes a string and return its length:

let fun x = String.length x;;

But it's showing syntax error. Why? If I just write String.length x;; it's fine but what's wrong in my function declaration?

How to pass string variable as argument to function in OCaml?

Answer 1

fun is a reserved keyword in OCaml. You can choose another name that's not a keyword and the function will work. Here's a list of reserved keywords in OCaml: https://caml.inria.fr/pub/docs/manual-ocaml/manual071.html

Answer 2

You are mixing different syntaxes here:

1. LET <ident> <ident>* = <expr>
2. FUN <ident>* -> <expr>

The "let" must be followed by the name of the function you want to create and "fun", being a reserved keyword, is not a valid name for the function. It's a keyword and not an identifyer so the syntax parser gives you an error.