Haskell int list to String

Question

I would like to know if there is a simple way to turn [5,2,10] into "52a". Where its not just to this case, I want to associate any number>9 with the corresponding letter.

Thanks in advance.

• Don Roby: What happens for numbers greater than 36?

Answer 1

You want to do something to each element of a list in order to get a new list. In other words, you want to apply a function (that you will have to define yourself) to each element. This is what the map function from the Prelude is for.

To convert between integers and individual characters, you could use the chr and ord functions from the Data.Char module.

So,

map (\i -> if i < 10 then chr (i + ord '0') else chr (i - 10 + ord 'a'))

is a function of type [Int] -> String that does what you want (no error checking included, though).

• wolfgang: At least on GHC, the chr function will throw an exception when its argument is outside the legal range for unicode Chars (0 .. 0x10FFFF). Things will look rather... creative... long before that.

Answer 2

Slower but more elegant:

f = map ((['0'..'9'] ++ ['a'..'z']) !!)

If your numbers are 0-15 use map intToDigit from Data.Char.