[tomp]

No, it’s actually because , (comma) denotes a tuple.

    [1, 2; 3, 4]

is a list of tuples, of type (int * int) list, equivalent to

    [(1, 2); (3, 4)]

[Athas]

I never understood the motivation for allowing tuples without surrounding parens. There are a few very simple functions that look cuter this way, but it constantly trips me up in more complex situations.

[a-nikolaev]

No parentheses can be nice for cleaner pattern matching, e.g. something like this:

  match a, b with
  | 1, 2 -> x
  | _ -> y

[cwzwarich]

This phenomenon is actually another example of the phenomenon he mentions. In strict precedence parsing, operators are assigned meaning rather than productions of a grammar (which would could those operators in distinct contexts), so once you've decided a comma indicates a tuple, it's easier to just allow this syntax.

[goodoldneon]

The "comma makes a tuple" behavior is a big gotcha I've experienced in Python. I wish that behavior didn't exist

[LynxInLA]

Which version of that are you talking about in Python? The biggest related gotcha I've seen in Python is when you have a trailing comma `x = 1,` and accidentally create a tuple.

[goodoldneon]

Yea that’s the most common gotcha