How to use assert in OCaml?

Question

I am trying to learn OCaml and I am having trouble with the assertion statement. In the interpreter I can use it: ``` Zameers-MacBook-Air:~ zmanji$ ocaml OCaml version 4.01.0 # let x = 1;; val x : int = 1 # assert(x > 2);; Exception: Assert_failure ("//toplevel//", 1, 0). # ^D ``` However when I put the code in a file that looks like this: ``` let x = 1 assert(x > 2) ``` I get the following error: ``` Zameers-MacBook-Air:Q4 zmanji$ ocaml test.ml File "test.ml", line 2, characters 0-6: Error: Syntax error ``` What am I doing wrong?

Accepted Answer

If you put the `;;` in the file it will work. Without that, it doesn't make sense syntactically. An expression `1` followed by the keyword `assert` doesn't make sense.

I don't particularly like using `;;` in actual code (not at top-level, i.e., the interpreter). If you wanted to avoid it too, you could write

```
let x = 1
let () = assert (x > 2)
```

How to use assert in OCaml?

Solution

Problem