$ ./flurry -iin -c "<><<>()<>[<>{{}}]()>[()()]{}{}{{<>()}}" 2 3
3 2
0

Lfold
nil = \cn. n = SK
cons = \htcn. t c (c n h)
= \htc. S (K (tc)) (\n. cnh)
= \htc. S (K (tc)) (S c (K h))
= \ht. S <SKt> (S S (K (K h)))
= {{<><<>(){}>[<[<><>]()()>{}]}}
listify = height {cons (t=arg; h=pop)} nil
= []{<><<>(){}>[<[<><>]()()>{}]}[<>()]

$ ./flurry -iin -c "[]{<><<>(){}>[<[<><>]()()>{}]}[<>()]{<{<({}){}>}{}>[<><<>()>]}[<>()]" 1 0 1 1

11

Rfold
nil = \cn. n = SK
cons = \htcn. ch(tcn) = \htc.S(K(ch))(tc)
= \ht.S(\c. S(K(ch))) t
= \h. S(\c. S(K(ch)))
= \h. S(\c.<SK>(ch))
= \h. S(S(K<SK>)(SI(Kh)))
= <S(S(K<SK>))(SI)K>
= <S(<SK><SK>)(SI)K>
= <<>[(<<>()>){}][<>{{}}]()>
listify = height (\t. S cons (K t) pop) nil
= []{<><<>[(<<>()>){}][<>{{}}]()>[(){}]{}}[<>()]

cons' = \htcn. c(tcn)h
= \htc. S (\n. c(tcn)) (Kh)
= \htc. S (S(Kc)(tc)) (Kh)
= \ht. S (\c. S (S(Kc)(tc))) (K(Kh))
= \ht. S (S(KS)(\c. S(Kc)(tc))) (<KK>h)
= \ht. S (S(KS)(\c. <SK>c(tc))) (<KK>h)
= \ht. S (S(KS)(S<SK>t)) (<KK>h)
= \ht. S(<SK>S(S<SK>t)) (<KK>h)
= {{<>[(<<>()>)<>[<>{}{}]][<()()>{}]}}

$ echo -n "Hello World!" | ./flurry -bnb -c "[]{<>[(<<>()>)<>[<>{}{}]][<()()>{}]}[<>()][(){({})}][<>()]"
!dlroW olleH

<> <<> () <> [<> {{}}] ()> [() ()] {} {} {{<> ()}}      | a b
<> <<> () <> [<> {{}}] ()> [() ()] b {} {{<> ()}}       | a
<> <<> () <> [<> {{}}] ()> [() ()] b a {{<> ()}}        |
<<> () <> [<> {{}}] ()> b [() () b] a {{<> ()}}         |
<<> () <> [<> {{}}]> [() b] [() () b] a {{<> ()}}       |
<<> () <>> [<> {{}} [() b]] [() () b] a {{<> ()}}       |
<<> ()> [<> [<> {{}} [() b]]] [() () b] a {{<> ()}}     |
<> [() [<> [<> {{}} [() b]]]] [() () b] a {{<> ()}}     |
() [<> [<> {{}} [() b]]] a [() () b a] {{<> ()}}        |