There are more types than just classes and kinds.
The kind Type can be implemented by anything defining the method has-instance?.
The colon : is special syntax for using instanceof.
Symbol.hasInstance isn't yet implemented in any JS engine.When declaring a local, use : to assert its type.
For function return types, write the type right after the \.
The Str and Num builtins act like String and Number but recognize primitives instead of the rarely-used object versions. There's also Bool and Sym.
number->string = \:Str _:Num "#_" || This should fail number->string []
You can also use value:Type (with no spaces) to call contains?.
For just :Type, the test is on _. (This works great in case expressions!)
. 1:Num . not 1:Str _ = "one" . not :Num . :Str
Pred-Type
Any predicate can become a Type.
name. adds an object property equal to
the current name being assigned to, in this case "Three".
Three = new Pred-Type name. predicate. \_ =? _ 3 . 3:Three . 4:Three
prefix
Mason code often uses prefixes and suffixes to indicate type.
The compiler doesn't treat these specially. msl follows this convention, but you don't have to.
| Looks like | Means |
?a | ? option |
$a | $ promise |
@a | @ collection |
a->b | Map from a to b |
a? | Bool |
An optional promise is ?$a; a promise for an option is $?a.
a! indicates a function that performs some action rather than just returning a value.