Why are functions in Ocaml/F# not recursive by default?

Question

Why is it that functions in F# and Ocaml (and possibly other languages) are not by default recursive?

In other words, why did the language designers decide it was a

Answer 1

Given this:

let f x = ... and g y = ...;;

Compare:

let f a = f (g a)

With this:

let rec f a = f (g a)

The former redefines f to apply the previously defined f to the result of applying g to a. The latter redefines f to loop forever applying g to a, which is usually not what you want in ML variants.

That said, it's a language designer style thing. Just go with it.