Non-decimal radices/Convert: Difference between revisions

=={{header|Haskell}}==

It's actually more useful to represent digits internally as numbers instead of characters, because then one can define operations that work directly on this representation.

So conversion to and from digits represented as 0-9 and a-z is done in an additional step.

<pre>

import Data.List

import Data.Char

toBase :: Int -> Int -> [Int]

toBase b v = toBase' [] v where

toBase' a 0 = a

toBase' a v = toBase' (r:a) q where (q,r) = v `divMod` b

fromBase :: Int -> [Int] -> Int

fromBase b ds = foldl' (\n k -> n * b + k) 0 ds

toAlphaDigits :: [Int] -> String

toAlphaDigits = map convert where

convert n | n < 10 = chr (n + ord '0')

| otherwise = chr (n + ord 'a')

fromAlphaDigits :: String -> [Int]

fromAlphaDigits = map convert where

convert c | isDigit c = ord c - ord '0'

| isUpper c = ord c - ord 'A' + 10

| isLower c = ord c - ord 'a' + 10

</pre>

Example:

<pre>

*Main> toAlphaDigits $ toBase 16 $ 42

"2a"

*Main> fromBase 16 $ fromAlphaDigits $ "2a"

42

</pre>