U.hs is a LISP syntax Unlambda implementation written in Haskell. Started initially as a programming homework. Now development still in progress. The language takes the idea from Unlambda:

• (Almost) everything is function. Functions are of type function -> function (and hence have no type at all).

However, important language sugars and modifications are made:

1. Lambda is introduced back, for the sake of any sane soul. A Lisp-style syntax is used. So I = ((S K) K).
2. Pure functional design, with referential transparency, lazy evaluation and CPS IO operation. There is no strictness nor delayed application.
3. Module system, standard library and syntax sugar for CPS.

U.hs conventionally assumes file extension .u. Example of helloworld.u:

(import io)
(def main (run
	(_ (io.putStrLn "hello world"))
	(exit 0)
	)
)

The "run" statement is syntax sugar for chaining callbacks: (run (a b) (c d) e) = (b (\a (d (\c e)))). All io functions use callback to get the return value. Program starts at main in the main module. Sub-modules are loaded recursively by the import statements.

To interpretively run the program call urun

$ghc urun.hs
$./urun helloworld.u
hello world

A basic repl calculator is also included.

$runghc urepl.hs
; type :q to quit, :? for help
>(+ 3 1)
4
>(putChar 'a' (\_ (putChar '\n' exit)))
a
>:q

TODO