How to print integer literals in binary or hex in haskell?

Question

How to print integer literals in binary or hex in haskell?

printBinary 5 => "0101"

printHex 5 => "05"

Which libraries/functions allow this?

I came across the Numeric module and its showIntAtBase function but have been unable to use it correctly.

> :t showIntAtBase 

showIntAtBase :: (Integral a) => a -> (Int -> Char) -> a -> String -> String

Answer 1

The Numeric module includes several functions for showing an Integral type at various bases, including showIntAtBase. Here are some examples of use:

import Numeric (showHex, showIntAtBase)
import Data.Char (intToDigit)

putStrLn $ showHex 12 "" -- prints "c"
putStrLn $ showIntAtBase 2 intToDigit 12 "" -- prints "1100"

Answer 2

You may also use printf of the printf package to format your output with c style format descriptors:

import Text.Printf

main = do

    let i = 65535 :: Int

    putStrLn $ printf "The value of %d in hex is: 0x%08x" i i
    putStrLn $ printf "The html color code would be: #%06X" i
    putStrLn $ printf "The value of %d in binary is: %b" i i

Output:

The value of 65535 in hex is: 0x0000ffff
The html color code would be: #00FFFF
The value of 65535 in binary is: 1111111111111111