Anonymous functions are a syntax for creating function objects on the fly without naming them.
# `->` is an anonymous function operator # same as `f x, y = x + y` f = (x, y) -> x + y # same as `g(x, y: Int): Int = x + y` g = (x, y: Int): Int -> x + y
You can omit the
() if there is only one argument.
assert [1, 2, 3].map_collect(i -> i + 1) == [2, 3, 4] assert ((i, j) -> [i, j])(1, 2) == [1, 2]
In the case below it is
0..9, (i -> ...) and not
(0..9, i) -> ....
-> takes only one argument on the left side. Multiple arguments are received as a single tuple.
for 0..9, i: Int -> ...
In anonymous functions, there is a difference in parsing due to whitespace.
# In this case, interpreted as `T(() -> Int)` i: T() -> Int # in this case it is interpreted as (U()) -> Int k: U() -> Int
Anonymous functions can be used without arguments.
# `=>` is an anonymous procedure operator p! = () => print! "`p!` was called" # `() ->`, `() =>` have syntax sugar `do`, `do!` # p! = do! print! "`p!` was called" p!() # `p!` was called
No-argument functions can be used for lazy initialization.
time = import "time" date = import "datetime" now = if! True: do!: time. sleep! 1000 date.now!() do date.new("1970", "1", "1", "00", "00")
You can also type and pattern match. Because of this, the
match function is mostly implemented with the power of anonymous functions.
Anonymous functions given as arguments to the
match function are tried in order from the top. So, you should describe the special cases at the top and the more general cases at the bottom. If you get the order wrong, the compiler will issue a warning (if possible).
n = (Complex or Ratio or Int).sample!() i = matchn: PI -> PI # if equal to constant PI For (i: 1..10) -> i # Int from 1 to 10 (i: Int) -> i # Int (c: Complex) -> c.real() # For Complex. Int < Complex, but can fallback _ -> panic "cannot convert to Int" # If none of the above apply. match must cover all patterns
Error handling is also generally done using
res: ParseResult Int matchres: i: Int -> i err: Error -> panic err.msg res2: Result Int, Error match res2: ok: Not Error -> log Type of ok err: Error -> panic err.msg
Anonymous polymorphic functions
# same as id|T| x: T = x id = |T| x: T -> x