The Main Function
The entry point of any Flix program is the main
function which must have the signature:
def main(): Unit \ IO
That is, the main function
- must return
Unit, and - must be
Impure(marked with annotation\ IO).
The signature of main does not specify any
arguments, but the command line arguments passed to
the program can be accessed by calling
Environment.getArgs().
def main(): Unit \ IO =
let args = Environment.getArgs();
...
Flix requires main to be Impure.
If main was pure there would be no reason to run the
program.
Typically the impurity requirement is satisfied
because main prints to the console or has another
side-effect.