syn.cat

true  = "T"
false  = "F"
zero  = "0"
succ x = cat "S" x
pred x = let "S0" "0" x
add x y = let "0" y x
sub x y = let y "0" x
mul x y = let "S" let "0" "" y x
dr x y z = let y x let x y z
encode s = cat cat "_^" let "$" "\$" let "^" "\^" let "\" "\\" s "_$"
decode s = let "\\" "\" let "\$" "$" let "\^" "^" let "_^" "" let "_$" "" s
eq x y = let encode x "F" let encode y "T" encode x
if c x y = decode let "T$" encode x let "F$" encode y cat c "$"
in x y = not eq y let x "" y
not x = if x false true
ife x = eq x ""
digit x = let "1" "S0" let "2" "SS0" let "3" "SSS0" let "4" "SSSS0" let "5" "SSSSS0" let "6" "SSSSSS0" let "7" "SSSSSSS0" let "8" "SSSSSSSS0" let "9" "SSSSSSSSS0" x
exp x y = ! cat let "S" "mul " let "S0" "" y let " 0" "" let "S" cat cat `"` x `" ` y
nrep x p = let "0" p let "1" p let "2" p let "3" p let "4" p let "5" p let "6" p let "7" p let "8" p let "9" p x
len x = cat nrep x "S" "0"
ten  = succ digit "9"
revdigit x = let "S0" "1" let "SS0" "2" let "SSS0" "3" let "SSSS0" "4" let "SSSSS0" "5" let "SSSSSS0" "6" let "SSSSSSS0" "7" let "SSSSSSSS0" "8" let "SSSSSSSSS0" "9" x
head x = pred cat nrep let "$0" "S" let "$1" "SS" let "$2" "SSS" let "$3" "SSSS" let "$4" "SSSSS" let "$5" "SSSSSS" let "$6" "SSSSSSS" let "$7" "SSSSSSSS" let "$8" "SSSSSSSSS" let "$9" "SSSSSSSSSS" cat "$" x "" "0"
num x = ! if eq len x "S0" spack digit x cat cat cat cat cat cat cat `add mul "` head x `" exp ten "` pred len x `" ` `num "` let cat "$" revdigit head x "" cat "$" x `"`
spack x = cat cat `"` x `"`
leq x y = in x y
show x = ! if leq len x digit "9" spack revdigit x cat cat cat cat `cat show "` let "SSSSSSSSSS" "S" sub x let "SSSSSSSSSS" "" x `" revdigit "` let "SSSSSSSSSS" "" x `"`
fib x = if eq x zero zero ! if leq x num "2" spack num "1" "add fib pred x fib pred pred x"