Hume (programming Language) - Example

Example

{- example file fibo-i.hume -} -- declarations type Int = int 32 ; exception EIncredible :: (Int, string) ; exception EIllegalArgument :: string ; -- expression language (eager evaluation) fibo :: Int -> Int ; fibo 0 = 1; fibo 1 = 1; fibo n = if n < 0 then raise EIllegalArgument "fibo: negative argument: " ++ (n as string) else fibo (n-1) + fibo (n-2); -- fibo bounded in time bfibo :: Int -> Int ; bfibo n = (fibo n) within 10ms ; -- evaluation time restriction -- raises Timeout (interpreter only) -- automata as stateless boxes -- the state is kept by feedback into the mailboxes box fib -- tuple of inputs, single element mailboxes in (n::integer, flag::integer) -- tuple of named outputs out (nextn::integer, flag'::integer, result::(integer, integer, string)) -- within 500KB (400KB) -- heap and stack cost boundings (compiler only) -- would throw HeapOverflow, StackOverflow handles Timeout, EIncredible, EIllegalArgument -- declares handled exceptions match -- pattern for the tuple of inputs -> expression_with_type_of_the_''out''_tuple -- * wildcards for unfilled outputs, and unconsumed inputs (n, 0) -> if n >= 99 then raise EIncredible (n, " reached") else let calc = bfibo n in (n+1, 0, (n, calc, "\n")) | (n, 1) -> (n, 0, (n, *, " Timeout thrown\n")) | (n, 2) -> (n, 0, (n, *, " EIncredible thrown\n")) handle -- exception_pattern -> expression_with_type_of_the_''out''_tuple Timeout -> ( 0, 1, (*, *, "Timeout caught, we restart n to 0\n")) | EIncredible (n, msg) -> (0, 2, (*, *, "Incredible: " ++ (n as string) ++ msg ++ ", we restart n to 0\n")) | EIllegalArgument msg -> (0, 0, (*, *, "Illegal argument: " ++ msg ++ "\n")) ; -- connections stream output to "std_out"; wire fib -- fib ''in'' tuple match with origins qualified named outputs and sources (fib.nextn initially 0, fib.flag' initially 0) -- fib ''out'' tuple match with destination mailboxes and sinks (fib.n, fib.flag, output) ;