Displaying a number in another base

Strings are a natural way to represent numbers in different bases due to the inclusion of letters as digits. This recipe will tell us how to convert a number to a string that can be printed as output.

How to do it...

1. We will need to import the following two functions:

   import Data.Char (intToDigit, chr, ord) 
   import Numeric (showIntAtBase)

2. Define a function to represent a number in a particular base as follows:

   n 'inBase' b = showIntAtBase b numToLetter n ""

3. Define the mapping between numbers and letters for digits larger than nine as follows:

   numToLetter :: Int -> Char
   numToLetter n
     | n < 10 = intToDigit n
     | otherwise = chr (ord 'a' n – 10)

4. Print out the result using the following code snippet:

   main :: IO ()
   main = do
     putStrLn $ 8 'inBase' 12
     putStrLn $ 10 'inBase' 12
     putStrLn $ 12 'inBase' 12
     putStrLn $ 47 'inBase' 12

5. The following is the printed output when running the code:

   $ runhaskell Main.hs
   
   8
   a
   10
   3b
   

How it works...

The showIntAtBase function takes in a base, the desired number, and its mapping from number to printable digit. We order our digits in the following manner: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, a, b, c, d, e, f, and so on, up to 36 characters. Putting it all together, we get a convenient way to represent a decimal number in any base.

See also

To read a string representing a number from another base as a decimal integer, refer to the Reading a number from another base recipe.