implementation module get_dictionary

import StdEnv
import StdDynamic

:: TVD a 	= CVD a & get_dictionary a
:: TD a 	= CD & get_dictionary a

cvd_to_td :: (TVD a) -> TD a;
cvd_to_td (CVD a) = CD;

select_dictionary :: ![Int] !(TVD a) -> Dynamic
select_dictionary s d=:(CVD _)
	= get_dictionary s (cvd_to_td d)

class get_dictionary a | TC, Eq a :: ![Int] !(TD a) -> Dynamic

instance get_dictionary Int where
	get_dictionary [] x
		= dynamic x

instance get_dictionary (a,b) | get_dictionary a & get_dictionary b where
	get_dictionary [] x
		= dynamic x
	get_dictionary [e:s] x
		| e==0
			= get_dictionary s (f0 x)
		| e==1
			= get_dictionary s (f1 x)
	where
		f0 :: (TD (a,b)) -> TD a | get_dictionary a
		f0 CD = CD

		f1 :: (TD (a,b)) -> TD b | get_dictionary b
		f1 CD = CD

instance get_dictionary [a] | get_dictionary a where
	get_dictionary [] x
		= dynamic x
	get_dictionary [0:s] x
		= get_dictionary s (f x)
	where
		f :: (TD [a]) -> TD a | get_dictionary a
		f CD = CD

Start
	# v = CVD ((0,[1]),2)
	# d0 = select_dictionary [] v
	# d1 = select_dictionary [0] v
	# d2 = select_dictionary [0,1] v
	# d3 = select_dictionary [0,1,0] v
	= (d0,'\n',d1,'\n',d2,'\n',d3)