Functions #

Functions in Slow are declared using the func keyword. A function can have zero or more arguments and returns null by default unless a return statement is included.

The syntax for declaring a function is func <name>(<arg1>, <arg2>, <etc>) followed by its body enclosed in curly brackets.

func isFactor(x, y) {
  return x % y == 0
}

Like everything in Slow, functions are also values and can be treated as such.

-> func mysteryFunc(x) { return x % 2 == 0 }
<func mysteryFunc>
-> var isEven = mysteryFunc
<func mysteryFunc>
-> isEven(2)
true

Defer Statements #

Inside a function, a function call can be deferred so that it runs just before the function exits, instead of wherever in the body the defer statement is (like Go’s defer statement). Statements are accrued but not evaluated as the function’s body executes and before the function exits, they are run. Deferred functions are currently not run if the function throws an error. This behavior will likely be added in the future.

-> func foo() {
..   # without the deferral, this statement would error because the variable does not yet exist
..   defer print(i)
..   var i = 0
..   for _ in :20 {
..     ++i
..   }
.. }
-> foo()
20