Sha256: cdb3c29c827f7042871862dfc3f0a13f4100704ec1f2f7aafc02156d1a5fc782
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Versions: 262
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Contents
exception NonBinaryDigitFound
exception EmptyBinaryStringFound
(* accepts a binary string and converts it to the decimal equivalant *)
fun binaryToDecimal n = let
val digits = List.map (fn c => (ord c) - 48) (explode n)
val len = List.length digits
fun validateBinaryDigits [] = true
| validateBinaryDigits (d::ds) = if d <> 0 andalso d <> 1 then false
else validateBinaryDigits ds
fun even n = (n mod 2) = 0
fun expt a b = let
fun loop x 0 acc = acc
| loop x 1 acc = x * acc
| loop x n acc = if (even n) then loop (x * x) (n div 2) acc
else loop (x * x) ((n - 1) div 2) (x * acc)
in
loop a b 1
end
fun f' [] mult acc = acc
| f' (x::xs) mult acc = f' xs (mult - 1) (acc + (x * (expt 2 mult)))
in
if len = 0 then raise EmptyBinaryStringFound
else if (validateBinaryDigits digits) then f' digits (len - 1) 0
else raise NonBinaryDigitFound
end
Version data entries
262 entries across 262 versions & 1 rubygems