OCaml delimiters and scopes
- by Jack
Hello!
I'm learning OCaml and although I have years of experience with imperative programming languages (C, C++, Java) I'm getting some problems with delimiters between declarations or expressions in OCaml syntax.
Basically I understood that I have to use ; to concatenate expressions and the value returned by the sequence will be the one of last expression used, so for example if I have
exp1; exp2; exp3
it will be considered as an expression that returns the value of exp3. Starting from this I could use
let t = something in exp1; exp2; exp3
and it should be ok, right?
When am I supposed to use the double semicol ;;? What does it exactly mean?
Are there other delimiters that I must use to avoid syntax errors?
I'll give you an example:
let rec satisfy dtmc state pformula =
match (state, pformula) with
(state, `Next sformula) ->
let s = satisfy_each dtmc sformula
and adder a state =
let p = 0.;
for i = 0 to dtmc.matrix.rows do
p <- p +. get dtmc.matrix i state.index
done;
a +. p
in
List.fold_left adder 0. s
| _ -> []
It gives me syntax error on | but I don't get why.. what am I missing? This is a problem that occurs often and I have to try many different solutions until it suddently works :/
A side question: declaring with let instead that let .. in will define a var binding that lasts whenever after it has been defined?
What I basically ask is: what are the delimiters I have to use and when I have to use them. In addition are there differences I should consider while using the interpreter ocaml instead that the compiler ocamlc?
Thanks in advance!
