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

If you import the Numeric and Data.Char modules, you can do this:

showIntAtBase 2 intToDigit 10 "" => "1010"
showIntAtBase 16 intToDigit 1023 "" => "3ff"

This will work for any bases up to 16, since this is all that intToDigit works for. The reason for the extra empty string argument in the examples above is that showIntAtBase returns a function of type ShowS, which will concatenate the display representation onto an existing string.

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

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"