Planned Features #

The features listed below are not yet implemented but are planned and may include proposed syntax.

Ternary Conditional Operator #

Slow will support a ternary conditional operator of the form <condition> ? <value if true> : <value if false>. Only one branch of the operator is ever evaluated.

# In the example below, if i is even, only f is called, otherwise
# only g is called.
var x = i % 2 == 0 ? f() : g()

Generators #

func myRange(stop) {
  for i in range(stop) {
    yield i
  }
}

for i in myRange(20) {
  print(i)
}

List Slicing #

l[0:2]
l[1:]
l[:2]
l[:-1]
l[-2:]

Enums #

enum Digit {
  ONE,
  TWO,
  THREE,
  FOUR,
}

Comprehensions #

var l2 = [2 * i for i in l if i % 2 == 0]
var m2 = {i: 2 * i for i in l}

for i in (2 * i for i in l) {
  print(i)
}

Classes #

class MyClass {
  var publicInts = []

  private var someInts = []

  private readonly var aValue = "foo"

  func :init(firstInt) {
    this.someInts.append(firstInt)
  }

  func :str() {
    return "<MyClass>"
  }

  func add(anotherInt) {
    this.someInts.append(anotherInt)
  }
}

var c = MyClass(1)

String Interpolation and Formatting #

var name = "John"
print("Hello, {{ name }}")
var aFloat = 1.0000000003
print("{{ aFloat:.3f }}")

Error Throwing and Handling #

try {
  throw Error()
} catch {
  handleError()
}

Variadic and Keyword Function Arguments #

func foo(x, y = 2, *args, **kwargs) {
  ...
}

List and Map Destructuring #

var [a, b, c] = [1, 2, 3]
var {d, e, f} = {"d": 4, "e": 5, "f": 6}

Sets #

Both mutable and immutable variants.

Underscore Assignment #

Values that should be ignored in an assignment statement or function definition can be named with the _ character. _ is not a variable but syntactic sugar to tell the interpreter to ignore the value.

var [a, _, _, d] = [1, 2, 3, 4]

func foo(a, _, b, _) {
  # ...
}