Literals
Numbers
1 -23 123'456
// some integer values of type Int64
1i32 -23i32 123'456i32
// some integer values of type Int32
1.0 -23.0 123'456.0
// some floating-point values of type Float64
1.0f32 -23.0f32 123'456.0f32
// some floating-point values of type Float32
Booleans
true false
// the two values of type Bool
Strings
"abc" ""
// some values of type String
Definitions
Constants
let a = 1
// the Int64 value 1 assigned to the constant a
a
1
a = 2
// compilation error – a constant cannot be reassigned
Variables
var a = 1
// the Int64 value 1 assigned to the variable a
a
1
a = 2 * 3
6
Functions
fun sum(a: Int64, b: Int64): Int64 = a + b
// a function accepting two arguments of type Int64
// and returning a value of type Int64
sum(12, 23)
35
Classes
class Person(let firstName: String, let lastName: String, var age: Int64) {
fun fullName: String = "${self.firstName} ${self.lastName}"
}
let alice = Person("Alice", "Smith", 23)
alice.lastName
"Smith"
alice.fullName
"Alice Smith"
alice.age = 24
alice.age
24
Unions
union Pet of Cat, Dog // types Cat and Dog defines elsewhere
Static methods
class Utilities {
@static
fun appendTest(value: String): String = "${value} test"
}
Utilities.appendTest("string")
"string test"
Control Flow
Conditions
let a = 2
if a == 1 { println("a is one") } else { println("a is not one") }
a is not one
fun describeFloat(float: Float64): String =
if float
... === Float64.NaN { "nonumber" }
... .isFinite.not { "infinity" }
... >= 0.0 { "positive" }
else { "negative" }
describeFloat(123.4)
"positive"
describeFloat(1.0/0.0)
"infinity"
Loops
for i in List[Int64](1, 2, 3) {
print(i.toString)
}
"123"
Operators
From strongest precedence to weakest:| Precedence | Operator |
|---|---|
| 1 | */& |
| 2 | +-|^ |
| 3 | ==!=<<=>>====!== |
| 4 | && |
| 5 | || |
Basic Types
Numbers
1 + 1
2
23.0 + 42.0 / -2.0
-44.0
23.0.toInt64 * 3
69
Booleans
true.not
false
true && false
false
true || false
true
Strings
let a = "foo"
"foo"
let c = a + "bar"
"foobar"
c.size
6
c.isEmpty
false
c.contains("oba")
true
c.startsWith("f")
true
Options
let some = Some[String]("value")
Some("value")
let none = None[String]()
None
some.isSome
true
none.isSome
false
some.contains("value")
true
some.contains("other")
false
none.contains("value")
false
Collection Types
Lists
let list = List[Int64](30, 10, 20, 40)
List(30, 10, 20, 40)
list.size
4
list(0) // same as list.get(0)
30
list(0) = 5 // same as list.set(0, 5)
List(5, 10, 20, 40)
list.first
Some(5)
list.last
Some(40)
d.removeAt(3)
List(5, 10, 20)
d.push(40)
List(5, 10, 20, 40)
Set
let set = HashSet[String]("hello", "goodbye")
HashSet("hello", "goodbye")
set.contains("hello")
true
set("hello") // same as set.get("hello")
Some("hello")
set.insert("ciao")
None
set.remove("ciao")
Some("ciao")
Maps
let map = HashMap[String, String](("hello", "a greeting"), ("goodbye", "a parting"))
HashMap(("hello", "a greeting"), ("goodbye", "a parting"))
map.contains("hello")
true
map.get("hello")
Some("a greeting")
map.insert("ciao", "not sure ...")
None
map.remove("ciao")
Some("not sure ...")
Array
let array = Array[Int64](30, 10, 20, 40)
Array(30, 10, 20, 40)
array.size
4
array(0) // same as array.get(0)
30
array(0) = 5 // same as array.set(0, 5)
List(5, 10, 20, 40)
array.first
Some(5)
array.last
Some(40)