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implementation module StdStack
import StdEnv
import StdList
:: Stack a :== [a]
newStack :: (Stack a)
newStack = []
push :: a (Stack a) -> (Stack a)
push a s = [a] ++ s
pop :: (Stack a) -> (Stack a)
pop [a:s] = s
pop [] = []
popn :: Int (Stack a) -> (Stack a)
popn 0 s = s
popn n s = popn (n-1) (pop s)
pushes :: [a] (Stack a) -> (Stack a)
pushes [] s = s
pushes a s = pushes (tl a) (push (hd a) s)
top :: (Stack a) -> a
top [] = abort "`top s` with s = []"
top s = hd s
topn :: Int (Stack a) -> [a]
topn n s
| n > length s = abort "`topn n s` with n > length s"
| otherwise = take n s
count :: (Stack a) -> Int
count s = length s
elements :: (Stack a) -> [a]
elements s = s
Start = ( "s0 = newStack = ", s0,'\n'
, "s1 = push 1 s0 = ", s1,'\n'
, "s2 = pushes [2..5] s1 = ",s2,'\n'
, "s3 = pop s2 = ", s3,'\n'
, "s4 = popn 3 s3 = ", s4,'\n'
, "s5 = top s4 = ", s5,'\n'
, "s6 = topn 3 s2 = ", s6,'\n'
, "s7 = elements s2 = ", s7,'\n'
// , "s8 = push 10 s1 = ", s8,'\n'
// , "s9 = popn 10 s8 = ", s9,'\n'
// , "sa = topn 5 s4 = ", sa,'\n'
// , "sb = top s0 = ", sb,'\n'
)
where
s0 = newStack
s1 = push 1 s0
s2 = pushes [2..5] s1
s3 = pop s2
s4 = popn 3 s3
s5 = top s4
s6 = topn 3 s2
s7 = elements s2
// s8 = push 10 s1
// s9 = popn 10 s8
// sa = topn 5 s4
// sb = top s0
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