Appendix A: Keywords
The following list contains keywords that are reserved for current or future use by the Halcyon language. As such, they cannot be used as identifiers.
Keywords Currently in Use
The following is a list of keywords currently in use, with their functionality described.
| Keyword | Use | Example |
|---|---|---|
module, end | Declares the beginning and end of a module respectively | module demo = ... end |
import | Imports a function from another language, such as JavaScript or C | |
let | Defines a variable | let myint = 5 |
do | Executes an expression (like a main function) | do string::print "Hi" |
type | Defines a new type, or type alias | type twoints = (std::int, std::int) |
match, with | Matches a discriminant with one or more patterns | match myint with |4 => ... |5 => ... |
if,then,else | Evaluates to a value based on a boolean expression | if myint == 5 then ... else ... |
fn | Declares a function | let myfn = fn a => a + 1 |
of | Denotes types that a constructor name contains | type result = fn A B => Ok of A | Error of B |
in | Limits a variable's scope to the next expression | let myint = 5 in let mynewint = myint + 1 |