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|
{-# LANGUAGE Arrows #-}
foo
f
g
h
ma = proc (
(a, b),
(c, d),
(e, f)
) ->
do -- Begin do
(x,y) -- GHC parser fails if layed out over multiple lines
<- f -- Call into f
(a,
c) -- Tuple together arguments
(b,
d)
-< (b + 1, -- Funnel into arrow
d * b)
if
x `mod` y == 0 -- Basic condition
then case e -- Only left case is relevant
of Left (z,
w) -> \u -> -- Procs can have lambdas
let
v
= u -- Actually never used
^ 2
in
(returnA
-< -- Just do the calculation
(x + y * z))
else do
let u = x -- Let bindings bind expressions, not commands
-- Could pattern match directly on x
i <- case u of
0 -> (g . h -< u)
n -> (
(h . g
-< y) -- First actual use of y
)
returnA -< ()
-- Sometimes execute effects
if i > 0
then ma -< ()
else returnA -< ()
returnA -< (i +
x *
y) -- Just do the calculation
|
