Saptarshi Guha a écrit :
Hello,
I was wondering why recursive functions need to be specified with
"rec". According to Practical Ocaml, to "inform the compiler that the function
exists". But when entering the function definition, can't the compiler note that
the function is being defined so that when it sees the function calling itself,
it wont say "Unbound value f"?
Essentially, the fact that "rec" means anything is mostly due to the
fact that you want to be able to redefine stuff.
let f = fun x -> x + 1
let f x = f (f x)
is valid in ocaml, and you're function f is the function that adds 2.
whereas
let rec f x = f (f x)
has a completely different meaning.
If you avoided the use of rec, saying "if unbound, assume rec", then the
line
let f x = f (f x)
has two entirely different meaning, depending on whether f is defined
before or not.
That would be quite a chaotic feature.
Wouldn't one of way of detecting a recursive function would be to see
if the indeed the function calls itself?
No. Because you never know if you intended to call the function
recursively, or if you intended to call an homonymous function you
defined before.
All the best,
--
Guillaume Yziquel
http://yziquel.homelinux.org/
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