Hi,

On Tue, Feb 13, 2018 at 10:31 PM, Tim Leonard <Tim@timleonard.us> wrote:

> [...]
> type my_record = { field1 : bool; field2 : int };;
>
> let f x = { field1 =   match x with _ -> true  ; field2 = 2 };; (* this
> fails *)
>

This fails because OCaml overloads ';' in a few different ways,
significantly: (1) as a field separator in a record, and (2) as a
sequencing operator between two expressions. In case of ambiguity OCaml
parses as the latter, but you really meant the former.

(2) 'sequencing operator' means that something like:

let x = print_endline "Hi!"; 1

... will evaluate whatever is on the left of the ';', throw away its value
(in this case 'unit'), then evaluate whatever is on the right of the ';'
and return *its* value as the final value of the compound expression.

Regards,

Yawar