Keywords

This listing explains the usage of every Pony keyword.

Keyword	Usage
actor	defines an actor
as	conversion of a value to another Type (can raise an error)
be	behavior, executed asynchronously
box	default reference capability – object is readable, but not writable
break	to step out of a loop statement
class	defines a class
compile_error	will provoke a compile error
continue	continues a loop with the next iteration
consume	move a value to a new variable, leaving the original variable empty
do	loop statement, or after a with statement
else	conditional statement in if, for, while, repeat, try (as a catch block), match
elseif	conditional statement, also used with ifdef
embed	embed a class as a field of another class
end	ending of: if then, ifdef, while do, for in, repeat until, try, object, lambda, recover, match
error	raises an error
for	loop statement
fun	define a function, executed synchronously
if	(1) conditional statement
	(2) to define a guard in a pattern match
ifdef	when defining a build flag at compile time: ponyc –D "foo"
in	used in a for in - loop statement
interface	used in structural subtyping
is	(1) used in nominal subtyping
	(2) in type aliasing
iso	reference capability – read and write uniqueness
lambda	to make a closure
let	declaration of immutable variable: you can't rebind this name to a new value
match	pattern matching
new	constructor
object	to make an object literal
primitive	declares a primitive type
recover	removes the reference capability of a variable
ref	reference capability – object (on which function is called) is mutable
repeat	loop statement
return	to return early from a function
tag	reference capability – neither readable nor writeable, only object identity
then	(1) in if conditional statement
	(2) as a (finally) block in try
this	the current object
trait	used in nominal subtyping: class Foo is TraitName
trn	reference capability – write uniqueness, no other actor can write to the object
try	error handling
type	to declare a type alias
until	loop statement
use	(1) using a package
	(2) using an external library foo: use "lib:foo"
	(3) declaration of an FFI signature
	(4) add a search path for external libraries: use "path:/usr/local/lib"
var	declaration of mutable variable: you can rebind this name to a new value
val	reference capability – globally immutable object
where	when specifying named arguments
while	loop statement
with	ensure disposal of an object