I know you can convert a String to an number with read:
Prelude> read "3" :: Int
3
Prelude> read "3" :: Double
3.0
But how do you grab the String representation of an Int value?
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4 Answers
The opposite of read is show.
Prelude> show 3
"3"
Prelude> read $ show 3 :: Int
3
7 Comments
kennytm
@Lega: You may find this useful: haskell.org/hoogle/?hoogle=Int+-%3E+String.
CoR
@ KennyTM A LOT of people will find that link useful! A link alone is +1, but for showing how to use it... That's +10 Thanks :)
Jon Watte
Note that some organizations/standards strongly discourage the use of "show" because of its extreme polymorphism. A type-specific function (or, worst case, wrapper around show) would be helpful.
duplode
@JonWatte "Might", not "would". At the level of generality of this question, I don't think your suggestion is actionable.
lesolorzanov
Is there a way to do this manually without usyng system functions?
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Anyone who is just starting with Haskell and trying to print an Int, use:
module Lib
( someFunc
) where
someFunc :: IO ()
x = 123
someFunc = putStrLn (show x)
2 Comments
devdanke
@Arlind: As someone trying to learn Haskell I really appreciate an answer like this. I'm not trying to become a Haskell expert at this time. I'm just trying to get simple functions to work and show the results to the console. Later I can learn what is and isn't "idiomatic". Thanks for helping out a beginner :-)
An example based on Chuck's answer:
myIntToStr :: Int -> String
myIntToStr x
| x < 3 = show x ++ " is less than three"
| otherwise = "normal"
Note that without the show the third line will not compile.
Comments
You can use show:
show 3
What I want to add is that the type signature of show is the following:
show :: a -> String
And can turn lots of values into string not only type Int.
For example:
show [1,2,3]
Here is a reference:
https://hackage.haskell.org/package/base-4.14.1.0/docs/GHC-Show.html#v:show
answered Jul 16, 2021 at 13:14
Willem van der Veen
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