fact x =
    if x == 0 then 1
    else x * fact (x-1)

//or with pattern matching:
fact_alt 0 = 1
       | x = x * fact_alt (x-1)

fact 5      //=> 120
fact_alt 5  //=> 120

dotproduct (v1:Arr u64) (v2:Arr u64) -> u64 given len v1 == len v2 =
    ret = mut 0
    for i in indices v1 do
        ret += v1#i * v2#i
    ret

dotproduct [1, 2, 3] [4, 5, 6]   //=> 22
dotproduct [1, 2, 3] [4, 5]      //error, lengths aren't equal!

//A collection of elements of type 'e
trait Collection 'c 'e given 'c -> 'e
    push 'c 'e -> 'c
    len 'c -> usz
    get col:'c idx:usz -> 'e given idx < len col

trait Show 't
    to_string 't -> Str

//print_elem: c:'a i:usz -> Str given Collection 'a 'b, Show 'b, i < len c
print_elem c i =
    get c i |> to_string

//build system is implemented as a library
//with no syntax changes to the language itself
import Build, File

default_target "program"

target "program" =>
    depend_on "legacy_cpp"
    compile "driver.an"

target "legacy_cpp" =>
    cppfiles = glob "*.cpp"
    map cppfiles cxx
    link_with cppfiles

//print every line in the file
file = mut InFile "file.txt"
for line in file do
    print line

//or
map file print

//reading an integer from stdin:
n = read i32

//Or read directly from an xml-formatted file: 
n = file.read i32 "<value>{}</value>"

//in file.hpp
struct Triple {
    int first, second, third;

    Triple(int a, int b, int c) :
        first(a), second(b), third(c){}

    int firstPlus(int d) const {
        return first + d;
    }
}; //in driver.an
//call clang api to parse file and import functions
import Cpp "file.hpp"
t = Triple(1, 2, 3)
t.firstPlus t.third  //=> 4

//Automatically thunk-ify parameters with !lazy
!lazy
when LessThan a b c = a
   | EqualTo a b c = b
   | GreaterThan a b c = c

(ans, guess) = (42, 53)

//only "too high!" is outputted
when (compare guess ans)   \
    (print "too low!")     \
    (print "just right!")  \
    (print "too high!")