What does "open!" mean?

Question

I'm looking at an OCaml source file that begins with the following instruction:

open! MiscParser

I understand that open MiscParser means "open the MiscParser module", but I don't know what the exclamation mark means.

score 47 · Accepted Answer · edited Jul 27 '21 at 23:22

47

It's to avoid triggering warnings if the open shadows an exisiting identifier. See the manual.

edited Jul 27 '21 at 23:22

Ng Peng Nam Sean

45
3

answered Mar 24 '14 at 11:39

Daniel Bünzli

5,119
20
21

ethan xu · Answer 2 · 2020-07-06T01:55:41.963

3

Extending what Daniel said, it also tells the compiler to not warn if the open is not used anywhere in the code. One of the common things people do is to open! Core, since Core is such a useful library that one should just open it even they may not be using it.

edited Jul 06 '20 at 01:55

answered Jul 05 '20 at 20:26

ethan xu

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What does "open!" mean?

2 Answers2