Haven't been able to find much online documentation regarding begin/end in ocaml. I have two different pattern matches in the same function (which I want to be independent of each other), but vscode is parsing them to nest the second inside the first. I've tried surrounding the first pattern match in begin/end, but it's giving me syntax errors:
begin match c.r with (* first pattern match *)
| [ r1; r2; r3 ] ->
let _ = print_endline (String.make 1 r3.top) in end
match cl with (* second pattern match *)
| [] -> []
I get a red underline on end that says Syntax error after unclosed begin, expecting expr. I do not understand what this means, since I wrote end to close the begin, so why is the begin unclosed? The code compiles fine without the begin/end (except that it nests the second pattern match inside the first one). Thanks.
In OCaml begin/end is essentially identical to open/close parentheses. Inside you should have a well-formed expression (as in pretty much any programming language).
What you have inside your begin/end is not an expression, since it ends with in. A let expression looks like let pattern = expr1 in expr2. You are missing the second expression inside the begin/end.
What you should do (I think) is put begin/end around the inner match like this:
match c.r with
| [r1; r2; r3 ] ->
let _ = print_endline (String.make 1 r3.top) in
begin
match c1 with
| [] -> []
...
end
| ...
(This code doesn't make a lot of sense but I assume it's just an example.)
As another simplification you can change let _ = a in b to a; b if a is of unit type, as it is in your code.