Syntax for this playground is similar to that of Scala, with some simplifications and limitations. We provide a short syntax guide here.
| Declarations | ||
|---|---|---|
| Item | Example | Notes |
| enum |
enum Food[X] { case Apple[Y](X, Y) case Banana() } |
Enum names begin with a capital letter. Enums may have 0 or more type arguments in both the type and the cases. Case arguments are unnamed. |
| trait |
trait Food[X] { def calories(): Int def foobar[Y](x: X, y: Y): Int } |
Trait names begin with a capital letter. Traits may have 0 or more type arguments in both the type and the methods. |
| function |
def toString[X](x: X): String = { "a string" } |
Function names begin with a lowercase letter. Function declarations may have 0 or more type arguments. Their parameter and return types must be annotated. |
| Expressions | ||
| Item | Example | Notes |
| constant | true 123 |
The playground supports Boolean, integer, and string literals. |
| variable | x foo arg123 |
Variables begin with a lower-case letter. |
| binary operator | e + e e > e |
The playground supports arithmetic and comparison operators. |
| function application |
toString[Int](123) print("hello") |
Type parameters must be given explicitly. |
| pattern matching |
match e { case Food[String].Apple[Z](s, z) => e case Food[String].Banana() => e } |
Type parameters for the scrutinee type must be given explicitly. Case type parameters are quantified with a type variable. |
| enum construction | Food[Int].Apple[String](123, "abc") | Type parameters must be given explicitly. |
| method invocation |
obj.calories() obj.foobar[String](1, "str") |
Type parameters must be given explicitly. |
| object construction |
new Food[Bool] { def calories() = { 123 } def foobar[W](b, w) = { 456 } } |
Type parameters for the object type must be given explicitly. Method type parameters are quantified with a type variable. |
| if-then-else | if (e) { e } else { e } | |
| let-binding | let x = 123; x + 1 | |
| sequence | print("hello"); print("world") | |
| Types | ||
| Item | Example | Notes |
| base type | Int String Boolean |
|
| parameterized type | Food[Int] | Enums and traits can be parameterized with types. |
| type variable | X YETI ZOETROPE |
Type variables consist of all capital letters. |