Series of let definitions

Question

I'm a beginner in OCaml, and i have a problem with series of let, like:

let x = myFun y in
let z = myFun x in
...

But, between the lets, i use Hashtbl.iter and other functions that returns unit. If i do:

let x = myFun y in
Hashtbl.iter (...) ...
let z = myFun x in
...

The compiler raises an error. But, if i do:

let x = myFun y in
let h = Hashtbl.iter (...) ...
let z = myFun x in
...

The compiler don't raise any error, just warnings showing that "h" is never used. What's the best way to do that without any problem? Thanks.

Answer 1

You have to use ; to separate expressions:

e1 ; e2

This performs the side-effects in e1 and discards the result, and then evaluates `e2.

So in your case:

let x = myFun y in
Hashtbl.iter (...) ... ;
let z = myFun x in
...

Answer 2

Note that you can write

let x = ... in
  let _ = Hashtbl.iter in ...