> Also note you do not need "and". That is only required when the variables
> being defined are mutually recursive. It would be better style to write:
> 
> let x = 1;;
> let y = 2;;

The style aspect of your comment is a definite matter of opinion![*]

Given that this is a beginner question, it's probably worth clarifying that
in the context of "let .. and .. ;;" or "let .. and .. in ..;;" the "and" is
a shorthand allowing you to group multiple lets together without introducing
a new environment.

"and" only provides mutually recursive definitions in a "let rec" statement.


David



[*] I personally find it neater to group a series of definitions at the same
level using "let .. and .. in" and only use let again for nested definitions
but that's because I indent code after an "in" but I think that my indenting
scheme is somewhat less common...