String Formatting columns in Haskell without Text.Printf

Question

I am new to Haskell. I am at the last part of a school project. I have to take tuples and print them to an outfile and separate them by a tab column. So (709,4226408), (12965,4226412) and (5,4226016) should have and output of

709     4226408
12965   4226412
5       4226016

What I have been trying to do is this:

genOutput :: (Int, Int) -> String
genOutput (a,b) = (show a) ++ "\t" ++ (show b)

And this gives outputs like:

"709\t4226408"
"12965\t4226412"
"5\t4226016"

There are 3 things wrong with this. 1) Quotes still appear in the output. 2) The \t tab does not actually become a tab space. .Whenever I try to make an actual tab for the "" it just comes out as a " " space. 3) They are not aligned into columns like the above example. I know Text.Printf exists but we are not allowed to import anything other than:

import System.IO
import Data.List
import System.Environment

How are you printing the strings?

Joseph Sible-Reinstate Monica
– Joseph Sible-Reinstate Monica

2021-03-29 05:22:03 +00:00
Commented Mar 29, 2021 at 5:22 — Joseph Sible-Reinstate Monica
– Joseph Sible-Reinstate Monica, Commented Mar 29, 2021 at 5:22

Random Dev · Accepted Answer · 2021-03-29 06:13:19Z

that's the output you get from GHCi I guess? Try to use putStrLn instead:

Prelude> genOutput (1,42)                                      
"1\t42"                                                        
                                                               
Prelude> putStrLn $ genOutput (1,42)                    
1       42

Why is that?

If you tell GHCi to evaluate an expression it will do so and (more or less) output it using show - show is designed to work with read and will usually output a value as if you would input it directly into Haskell. For a String that will include escape sequences and the "s

Now using putStrLn it will take the string and print it to stdout as you would expect.

Using `print`

Another reason could be that you use print to output your value - print is show + putStrLn so it'll show the values first re-introducing the escapes (as GHCi would) - so if you use print change it to putStrLn if you are using Strings

Collectives™ on Stack Overflow

String Formatting columns in Haskell without Text.Printf

1 Answer 1

Why is that?

Using `print`

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Why is that?

Using print

Comments

Your Answer

Sign up or log in

Post as a guest

Related

Using `print`